## 1. Introductory Remarks



While it is in the nature of philosophical movements and their leading
doctrines to court controversy, the Vienna Circle and its philosophies
did so more than most. To begin with, its members styled themselves as
conceptual revolutionaries who cleared the stables of academic
philosophy by showing metaphysics not simply to be false, but to be
cognitively empty and meaningless. In addition, they often associated
their attempt to overcome metaphysics with their public engagement for
scientific Enlightenment reason in the ever-darkening political
situation of 1920s and 1930s central Europe. Small wonder then that
the Vienna Circle has sharply divided opinion from the start. There is
very little beyond the basic facts of membership and its record of
publications and conferences that can be asserted about it without
courting some degree of controversy. (For English-language survey
monographs and articles on the Vienna Circle, see Kraft 1950,
Jorgensen 1951, Ayer 1959b, Passmore 1967, Hanfling 1981, Stadler
1998, Richardson 2003. Particularly rich in background and
bio-bibliographical materials is Stadler 1997 [2015]. The best short
introductory book has remained untranslated: Haller 1993. For popular overviews see Sigmund 2015 [2018] and Edmonds [2020].)



Fortunately, more than three decades worth of recent scholarship in
history of philosophy of science now allows at least some disputes to
be put into perspective. (See, e.g., the following at least in part
English-language collections of articles and research monographs:
Haller 1982, McGuinness 1985, Rescher 1985, Gower 1987, Proust 1989,
Zolo 1989, Coffa 1991, Spohn 1991, Uebel 1991, Bell and Vossenkuhl
1992, Sarkar 1992, Uebel 1992, Oberdan 1993, Stadler 1993, Cirera
1994, Salmon and Wolters 1994, Cartwright, Cat, Fleck and Uebel 1996,
Giere and Richardson 1996, Nemeth and Stadler 1996, Sarkar 1996,
Richardson 1998, Friedman 1999, Wolenski and Kohler 1999, Fetzer
2000, Friedman 2000, Bonk 2003, Hardcastle and Richardson 2003,
Parrini, Salmon and Salmon 2003, Stadler 2003, Awodey and Klein 2004,
Reisch 2005, Galavotti 2006, Carus 2007, Creath and Friedman 2007,
Nemeth, Schmitz and Uebel 2007, Richardson and Uebel 2007, Uebel 2007,
Wagner 2009, Manninen and Stadler 2010, McGuinness 2011, Symons, Pombo
and Torres 2011, Creath 2012, Wagner 2012, Dambock 2016,
Pihlstrom, Stadler and Weidtmann 2017, Schiemer 2017, Tuboly 2017, Carus 2018, Cat and Tuboly 2019, Makovec and Shapiro 2019.) What distinguishes these works from valuable
collections like Schilpp 1963, Hintikka 1975 and Achinstein and Barker
1979 is that the unspoken assumption, to have understood Vienna Circle
philosophy correctly enough so as to consider its consequences
straightforward, is questioned in the more recent
scholarship. Many other pieces of new Vienna Circle scholarship are
spread throughout philosophical journals and essay collections with
more systematic or wider historical scope; important work has also
been done in German, Italian and French language publications but here
must remain unreferenced.)



Two facts must be clearly recognized if a proper evaluation of the
Vienna Circle is to be attempted. The first is, that, despite its
relatively short existence, even some of the most central theses of
the Vienna Circle underwent radical changes. The second is that its
members were by no means of one mind in all important matters;
occasionally they espoused perspectives so radically at variance with
each other that even their ostensive agreements cannot remain wholly
unquestioned. Behind the rather thin public front, then, quite
different philosophical projects were being pursued by the leading
participants with, moreover, changing alliances. One way of taking
account of this is by speaking (as above) explicitly of the
philosophies (in the plural) of the Vienna Circle (and to avoid the
singular definite description) while using the expression
"Vienna Circle philosophy" (without an article) in a
neutral generic sense.



Recent scholarship has provided what the received view of Viennese
neopositivism lacks: recognition and documentation of the sometimes
sharply differentiated positions behind the generic surface. This does
not invalidate all previous scholarship, including some fundamental
criticisms of its positions, but it restores a depth to Vienna Circle
philosophy that was absent from the standard histories. The value of
this development must not be underestimated, for the recognition of
the Vienna Circle's sophisticated engagement with aspects of the
philosophical tradition and contemporaneous challenges calls into
question unwarranted certainties of our own self-consciously
post-positivist era. While there remains support for the view that
philosophical doctrines were held in the Vienna Circle that wholly
merited many of the standard criticisms to be cited below, there is
now also support for the view that in nearly all such cases, these
doctrines were already in their day opposed within the Circle itself.
While some of the Vienna Circle philosophies are dated and may even
be, as John Passmore once put it, as dead as philosophies can be,
others show signs of surprising vitality. Which ones these are,
however, remains a matter of debate.



The lead pursued in this article is provided by the comments of a
long-time associate of the Vienna Circle, C.G. Hempel, made in
1991:



> 
> When people these days talk about logical positivism or the Vienna
> Circle and say that its ideas are passe, this is just wrong.
> This overlooks the fact that there were two quite different schools of
> logical empiricism, namely the one of Carnap and Schlick and so on and
> then the quite different one of Otto Neurath, who advocates a
> completely pragmatic conception of the philosophy of science....
> And this form of empiricism is in no way affected by any of the
> fundamental objections against logical positivism.... (quoted in
> Wolters 2003, 117)
> 



While differing with Hempel's specific claim about how
the two "schools" divide, the aim here is to fill out his suggestive
picture by indicating what Schlick, Carnap and Neurath stand for
philosophically and why the different wings of the Vienna Circle 
require differentiated assessments. After reviewing the basic facts
and providing an overall outline of Vienna Circle philosophy (in sect.
2), this article considers various doctrines in greater detail by way
of discussing standard criticisms with the appropriate distinctions in
mind (in sect. 3). No comprehensive assessment of the Vienna Circle
and the work of its members can be attempted here, but some basic
conclusions will be drawn (in sect. 4).


## 2. The Basics: People, Activities and Overview of Doctrines


### 2.1 People



The Vienna Circle was a group of scientifically trained philosophers
and philosophically interested scientists who met under the (nominal)
leadership of Moritz Schlick for often weekly discussions of problems
in the philosophy of science during academic terms in the years from
1924 to 1936. As is not uncommon with such groups, its identity is
blurred along several edges. Not all of those who ever attended the
discussions can be called members, and not all who attended did so
over the entire period. Typically, attention is focused on long-term
regulars who gained prominence through their philosophical
publications, but even these do not in all cases fall into the period
of the Vienna Circle proper. It is natural, nevertheless, to consider
under the heading "Vienna Circle" also the later work of
leading members who were still active in the 1940s, 50s and 60s.
Finally, there is the so-called periphery of international contacts
and visitors that prefigured the post-World War II network of
analytical philosophers of science. In the present article the
emphasis will be placed on the long-term regulars whose contributions
will be followed, selectively, into the post-Schlick era.



According to its unofficial manifesto (see section 2.3 below), the
Circle had "members" and recognized others as
"sympathetic" to its aims. It included as members, besides
Schlick who had been appointed to Mach's old chair in Philosophy
of the Inductive Sciences at the University of Vienna in 1922, the
mathematician Hans Hahn, the physicist Philipp Frank, the social
scientist Otto Neurath, his wife, the mathematician Olga Hahn-Neurath,
the philosopher Viktor Kraft, the mathematicians Theodor Radacovic and
Gustav Bergmann and, since 1926, the philosopher and logician Rudolf
Carnap. (Even before World War I, there existed a similarly oriented
discussion circle that included Frank, Hahn and Neurath. During the
time of the Schlick Circle, Frank resided in Prague throughout, Carnap
did so from 1931.) Further members were recruited among
Schlick's students, like Friedrich Waismann, Herbert Feigl and
Marcel Natkin, others were recruited among Hahn's students, like
Karl Menger and Kurt Godel. Though listed as members in the
manifesto, Menger and Kraft later wanted to be known only as as
sympathetic associates, like, all along, the mathematician Kurt
Reidemeister and the philosopher and historian of science Edgar
Zilsel. (Karl Popper was never a member or associate of the Circle,
though he studied with Hahn in the 1920s and in the early 1930s
discussed its doctrines with Feigl and Carnap.) Over the years, other
participants (not listed in the manifesto) included other students of
Schlick's and Hahn's like Bela von Juhos, Josef
Schachter, Walter Hollitscher, Heinrich Neider, Rose Rand, Josef
Rauscher and Kathe Steinhardt, a secondary teacher, Robert
Neumann, and, as notable thinkers with independent connections, the
jurist and philosopher Felix Kaufmann (also a member of F.A. von
Hayek's "Geistkreis") and the innovative
psychologist Egon Brunswik (coming, like the even more loosely
associated sociologists Paul Lazarsfeld and Marie Jahoda, from the
pioneering Karl Buhler's University Institute of
Psychology).



Despite its prominent position in the rich, if fragile, intellectual
culture of inter-war Vienna and most likely due to its radical
doctrines, the Vienna Circle found itself virtually isolated in most
of German speaking philosophy. The one exception was its contact and
cooperation with the Berlin Society for Empirical (later: Scientific)
Philosophy (the other point of origin of logical empiricism). The
members of the Berlin Society sported a broadly similar outlook and
included, besides the philosopher Hans Reichenbach, the logicians Kurt
Grelling and Walter Dubislav, the psychologist Kurt Lewin, the surgeon
Friedrich Kraus and the mathematician Richard von Mises. (Its leading
members Reichenbach, Grelling and Dubislav were listed in the
Circle's manifesto as sympathisers.) At the same time, members
of the Vienna Circle also engaged directly, if selectively, with the
Warsaw logicians (Tarski visited Vienna in 1930, Carnap later that
year visited Warsaw and Tarski returned to Vienna in 1935). Probably
partly because of its firebrand reputation, the Circle attracted also
a series of visiting younger researchers and students including Carl
Gustav Hempel from Berlin, Hasso Harlen from Stuttgart, Ludovico
Geymonat from Italy, Jorgen Jorgensen, Eino Kaila, Arne
Naess and Ake Petzall from Scandinavia, A.J. Ayer from the UK, Albert
Blumberg, Charles Morris, Ernest Nagel and W.V.O. Quine from the USA,
H.A. Lindemann from Argentina and Tscha Hung from China. (The reports
and recollections of these former visitors--e.g. Nagel
1936--are of interest in complementing the Circle's
in-house histories and recollections which start with the unofficial
manifesto--Carnap, Hahn and Neurath 1929--and extend through
Neurath 1936, Frank 1941, 1949a and Feigl 1943 to the memoirs by
Carnap 1963, Feigl 1969a, 1969b, Bergmann 1987, Menger 1994.)



The aforementioned social and political engagement of members of the
Vienna Circle and of Vienna Circle philosophy for Enlightenment reason
had never made the advancement of its associates or protegees
easy in Viennese academia. From 1934 onwards, with anti-semitism
institutionalized and irrationalism increasingly dominating public
discourse, this engagement began to cost the Circle still more dearly.
Not only was the Verein Ernst Mach closed down early that year for
political reasons, but the ongoing dispersal of Circle members by
emigration, forced exile and death meant that after the murder of
Schlick in 1936 only a small rump was able to continue meetings for
another two years in Vienna. (1931: Feigl emigrated to USA; 1934: Hahn
died, Neurath fled to Holland, 1940 to UK; 1935: Carnap emigrated to
USA; 1936: Schlick murdered; 1937: Menger emigrated to USA, Waismann
to UK; 1938: Frank, Kaufmann, Brunswik, Bergmann emigrated to USA;
Zilsel, Rand to UK, later to USA; Hollitscher fled to Switzerland,
later to UK; Schachter emigrated to Palestine; 1940: Godel
emigrated to USA; see Dahms 1995 for a chronology of the exodus.) But
the end of the Vienna Circle as such did not mean the end of its
influence due to the continuing development of the philosophy of
former members (and the work of Kraft in post-World War II Vienna; on
this see Stadler 2008). Particularly through their work in American
exile (esp. Carnap at Harvard, Chicago and UCLA; Feigl at Iowa and
Minnesota; less so Frank at Harvard) and that of earlier American
visitors (esp. Quine, Nagel), as well as through the work of fellow
emigrees from the Berlin Society (esp. Reichenbach, Hempel) and
their students (Hilary Putnam, Wesley Salmon), logical empiricism
strongly influenced the post-World War II development of analytic
philosophy of science. By contrast, Waismann had little influence in
the UK where Neurath, already marginalized, had died in 1945. (The
full story of logical empiricism's acculturation in the English
speaking world remains to be written, but see Howard 2003, Reisch
2005, Uebel 2005a, 2010, Douglas 2009, and Romizi 2012 for considerations of
aspects of Vienna Circle philosophy early and/or late that were neglected in the process
and remained long forgotten.)


### 2.2 Activities



After its formative phase which was confined to the Thursday evening
discussions, the Circle went public in 1928 and 1929 when it seemed
that the time had come for their emerging philosophy to play a
distinctive role not only in the academic but also the public sphere.
In November 1928, at its founding session, Schlick accepted the
presidency of the newly formed Verein Ernst Mach (Association Ernst
Mach), Hahn accepted one of its vice-presidencies and Neurath and
Carnap joined its secretariat. Originally proposed by the Austrian
Freidenkerbund (Free Thinker Association), the Verein Ernst Mach was
dedicated to the dissemination of scientific ways of thought and so
provided a forum for popular lectures on the new scientific
philosophy. In the following year the Circle stepped out under its own
name (invented by Neurath) with a manifesto and a special conference.
The publication of "The Scientific World Conception: The Vienna
Circle", signed by Carnap, Hahn and Neurath and dedicated to
Schlick, coincided with the "First Conference for the
Epistemology of the Exact Sciences" in mid-September 1929,
organised jointly with the Berlin Society as an adjunct to the Fifth
Congress of German Physicists and Mathematicians in Prague (where
Frank played a prominent role in the local organising committee). (On
the production history and early reception of the manifesto see Uebel
2008.) A distinct philosophical school appeared to be emerging, one
that was dedicated to ending the previous disputes of philosophical
schools by dismissing them, controversially, as strictly speaking
meaningless.



Throughout the early and mid-1930s the Circle kept a high and
increasingly international profile with its numerous publications and
conferences. In 1930, the Circle took over, again together with the
Berlin Society, the journal *Annalen der Philosophie* and
restarted it under the name of *Erkenntnis* with Carnap and
Reichenbach as co-editors. (Besides publishing original articles and
sustaining lengthy debates, this journal featured selected proceedings
of their early conferences and documented the lecture series of the
Verein Ernst Mach and the Berlin Society as well as their
international congresses.) In addition, from 1928 until 1936, Schlick
and Frank served as editors of their book series "Schriften zur
wissenschaftlichen Weltauffassung" ("Writings on the
Scientific World Conception"), which published major works by
leading members and early critics like Popper, while Neurath
edited, from 1933 until 1939, the series
"Einheitswissenschaft" ("Unified Science"),
which published more introductory essays by leading members and
sympathisers. Conference-wise, the Circle organized, again with the
Berlin Society, a "Second Conference for the Epistemology of the
Exact Sciences" as an adjunct to the Sixth Congress of German
Physicists and Mathematicians in Konigsberg in September 1930
(where Reidemeister played a prominent role in the organization and
Godel first announced his incompleteness result in the
discussion) and then began the series of International Congresses on
the Unity of Science with a "Pre-Conference" just prior to
the start of the Eighth International Congress of Philosophy in Prague
in September 1934. This, their last conference in Central Europe, was
followed by the International Congresses of various sizes in Paris
(September 1935, July 1937), Copenhagen (June 1936), Cambridge,
England (July 1938), Cambridge, Mass. (September 1939), all in the
main organized by Neurath; a smaller last gathering was held in
Chicago in September 1941. By 1938 their collective publication
activity began to centre on a monumentally planned *International
Encyclopedia of Unified Science*, with Neurath as editor-in-chief
and Carnap and Charles Morris as co-editors; by the time of
Neurath's death in 1945, only 10 monographs had appeared and the
series was wound up in 1970 numbering 20 monographs under the title
"Foundations of the Unity of Science" (notably containing
Thomas Kuhn's *Structure of Scientific Revolutions*
amongst them).



Individually, the members of the Vienna Circle published extensively
before, during and after the years of the Circle around Schlick. For
some (Frank, Hahn, Menger, Neurath), philosophy was only part of their
scientific output, with numerous monographs and articles in their
respective disciplines (mathematics, physics and social science);
others (Schlick, Carnap, Feigl, Waismann) concentrated on philosophy,
but even their output cared relatively little for traditional concerns
of the field. Here it must be noted that two early monographs by
Schlick (1918/25) and Carnap (1928a), commonly associated with the
Vienna Circle, mostly predate their authors' participation there
and exhibit a variety of influences not typically associated with
logical positivism (see section 3.7 below). Moreover, important
monographs by Frank (1932), Neurath (1931a), Carnap (1934/37) and
Menger (1934) in the first half of the 1930s represent moves away from
positions that had been held in the Circle before and contradict its
orthodox profile. Yet the Circle's orthodoxy, as it were, is not
easily pinned down either. Schlick himself was critical of the
manifesto of 1929 and gave a brief vision statement of his own in
"The Turning Point in Philosophy" (1930). A long-planned
book by Waismann of updates on Wittgenstein's thought, to which
Schlick was extremely sympathetic, was never completed as originally
planned and only appeared posthumously (Waismann 1965; for earlier
material see Baker 2003). Comparison with rough transcripts of the
Circle's discussions in the early 1930s (for transcripts from
between December 1930 and July 1931 see Stadler 1997 [2015,
69-123]) suggest that Waismann's Wittgensteinian
"Theses", dated
to "around 1930" (Waismann 1967 [1979, Appendix B]), come closest
to an elaboration of the orthodox Circle position at that time (but
which remained not undisputed even then). Again, what needs to be
stressed is that all of the Circle's publications are to be
understood as contributions to ongoing discussions among its members
and associates.


### 2.3 Overview of Doctrines



Despite the pluralism of the Vienna Circle's views, there did
exist a minimal consensus which may be put as follows. A theory of
scientific knowledge was propagated which sought to renew empiricism
by freeing it from the impossible task of justifying the claims of the
formal sciences. It will be noted that this updating did not leave
empiricism unchanged.



Following the logicism of Frege and Russell, the Circle considered
logic and mathematics to be analytic in nature. Extending
Wittgenstein's insight about logical truths to mathematical ones
as well, the Circle considered both to be tautological. Like true
statements of logic, mathematical statements did not express factual
truths: devoid of empirical content they only concerned ways of
representing the world, spelling out implication relations between
statements. The knowledge claims of logic and mathematics gained their
justification on purely formal grounds, by proof of their derivability
by stated rules from stated axioms and premises. (Depending on the
standing of these axioms and premises, justification was conditional
or unconditional.) Thus defanged of appeals to rational intuition, the
contribution of pure reason to human knowledge (in the form of logic
and mathematics) was thought easily integrated into the empiricist
framework. (Carnap sought to accommodate Godel's
incompleteness results by separating analyticity from effective
provability and by postulating that arithmetic consisted of an
infinite series of ever richer arithmetical languages; see the
discussion and references in section 3.2 below.)



The synthetic statements of the empirical sciences meanwhile were held
to be cognitively meaningful if and only if they were empirically
testable in some sense. They derived their justification as knowledge
claims from successful tests. Here the Circle appealed to a criterion of meaningfulness
(cognitive significance) the correct formulation of which was problematical and much
debated (and will be discussed in greater detail in section 3.1
below). Roughly, if synthetic statements failed testability in
principle they were considered to be cognitively meaningless and to
give rise only to pseudo-problems. No third category of significance
besides that of *a priori* analytical and *a posteriori*
synthetic statements was admitted: in particular, Kant's
synthetic *a priori* was banned as having been refuted by the
progress of science itself. (The theory of relativity showed what had
been held to be an example of the synthetic *a priori*, namely
Euclidean geometry, to be false as the geometry of physical space.)
Thus the Circle rejected the knowledge claims of metaphysics as being
neither analytic and *a priori* nor empirical and synthetic.
(On related but different grounds, they also rejected the knowledge
claims of normative ethics: whereas conditional norms could be
grounded in means-ends relations, unconditional norms remained
unprovable in empirical terms and so depended crucially on the
disputed substantive *a priori* intuition.)



Given their empiricism, all of the members of the Vienna Circle also
called into question the principled separation of the natural and the
human sciences. They were happy enough to admit to differences in
their object domains, but denied the categorical difference in both
their overarching methodologies and ultimate goals in inquiry, which
the historicist tradition in the still only emerging social sciences
and the idealist tradition in philosophy insisted on. The
Circle's own methodologically monist position was sometimes
represented under the heading of "unified science".
Precisely how such a unification of the sciences was to be effected or
understood remained a matter for further discussion (see section 3.3
below).



It is easy to see that, combined with the rejection of rational
intuition, the Vienna Circle's exclusive apportionment of reason
into either formal *a priori* reasoning, issuing in analytic
truths (or contradictions), and substantive *a posteriori*
reasoning, issuing in synthetic truths (or falsehoods), severely
challenged the traditional understanding of philosophy. All members of
the Circle hailed the end of distinctive philosophical system
building. In line with the *Tractatus* claim that all
philosophy is really a critique of language, the Vienna Circle took
the so-called linguistic turn, the turn to representation as the
proper subject matter of philosophy. Philosophy itself was denied a
separate first-order domain of expertise and declared a second-order
inquiry. Whether the once queen of the sciences was thereby reduced to
the mere handmaiden of the latter was still left open. It remained a
matter of disagreement what type of distinctively
philosophical insight, if any, would remain legitimate. Just as
importantly, however, the tools of modern logic were employed also for
metatheoretical construction, not just for the reduction of empirical
claims to their observational base or, more generally, for the
derivation of their observational consequences. For the price of
abandoning foundationalist certainty this allowed for an enormous
expansion of the domain of empirical discourse. Ultimately, it opened
the space for the still ongoing discussions of scientific realism and
its alternatives (see section 3.4 below).



The Circle's leading protagonists differed in how they
conceptualized this reflexive second-order inquiry that the linguistic
turn had inaugurated. Nevertheless, they all agreed broadly that the
ways of representing the world were largely determined by convention.
A multitude of ideas hide behind this invocation of conventionality.
One particularly radical one is the denial of the apodicity of all
apriority, the denial of the claim that knowledge justified through
reason alone represents truths that are unconditionally necessary.
Another one is the imputation of agency in the construction of the
logico-linguistic frameworks that make human cognition possible, the
denial that conventionality could only mean acquiescence in tradition.
Whether such ideas were followed by individual members of the Circle,
however, depended on their own interests and influences. It is these
often overlooked or misunderstood differences that hold the key to
understanding the interplay of occasionally incompatible positions
that make up Vienna Circle philosophy. (As can be seen from some of
their internal disputes, moreover, these differences were also not
always obvious to the protagonists themselves.)



To see a striking example, consider their overarching conceptions of
philosophy itself. Some protagonists retained the idea that philosophy
possessed a separate disciplinary identity from science and, like
Schlick, turned philosophy into a distinctive, albeit non-formal
activity of meaning determination. Others, like Carnap, agreed on the
distinction between philosophy and science but turned philosophy into
a purely formal enterprise, the so-called logic of science. Still
others went even further and, like Neurath under the banner of
"unified science", also rejected philosophy as a separate
discipline and treated what remained of it, after the rejection of
metaphysics, as its partly empirical meta-theory, to be set beside the logic of science. With Schlick, then,
philosophy became the activity of achieving a much clarified and
deepened understanding of the cognitive and linguistic practices
actually already employed in science and everyday discourse. By
contrast, for Carnap, philosophy investigated and reconstructed
existing language fragments, developed new logico-linguistic
frameworks and suggested possible formal conventions for science,
while, for Neurath, the investigation of science was pursued by an
interdisciplinary meta-theory that encompassed empirical disciplines,
again with a pragmatic orientation. Thus we find in apparent
competition different conceptions of post-metaphysical philosophy: the
projects of experiential meaning determination, of formal rational
reconstruction and of naturalistic explications of leading theoretical
and methodological notions. (For roughly representative early
essay-length statements of their positions see Schlick 1930, Carnap
1932a and Neurath 1932a; later restatements are given in Schlick 1937,
Carnap 1936b and Neurath 1936b.) In the more detailed discussions
below these differences of overall approach will figure repeatedly
(see also section 3.6 below).



Criticisms of the basic positions adopted in the Vienna Circle are
legion, though it may be questioned whether most of them took account
of the sophisticated variations on offer. (Sometimes the
Circle's own writings are disregarded altogether and
"logical positivism" is discussed only via the proxy of
Ayer's popular exposition; see, e.g., Soames 2003.) But some
Neo-Kantians like Ernst Cassirer may claim that they too accepted
developments like the merely relative *a priori* and an
appropriate conception of the historical development of science.
Likewise, Wittgensteinians may claim that Wittgenstein's own
opposition to metaphysics only concerned false attempts to render it
intelligible: his merely ineffable but uneliminated metaphysics
concerned precisely what for him were essentials of ways of
representing the world. The commonest criticisms, however, concerned
not the uniqueness of the Vienna Circle's doctrines, or their
faithfulness to their supposed sources, but whether they were tenable
at all. Prominent objects of this type of criticism include the
verificationist theory of meaning and its claimed anti-metaphysical
and non-cognitivist consequences as well as its own significance; the
reductionism in phenomenalist or physicalist guises that appeared to
attend the Circle's attempted operationalisation of the logical
atomism of Russell and Wittgenstein; and the Circle's alleged
scientism in general and their formalist and a-historical conception
of scientific cognition in particular. These criticisms are discussed
in some detail below in order to assess why which of the associated
doctrines remain of what importance.



As noted, the Vienna Circle did not last long: its philosophical
revolution came at a cost. Yet what was so socially, indeed
politically, explosive about what appears on first sight to be a
particularly arid, if not astringent, doctrine of specialist
scientific knowledge? To a large part, precisely what made it so
controversial philosophically: its claim to refute opponents not by
proving their statements to be false but by showing them to be
(cognitively) meaningless. Whatever the niceties of their
philosophical argument here, the socio-political impact of the Vienna
Circle's philosophies of science was obvious and profound. All
of them opposed the increasing groundswell of radically mistaken,
indeed irrational, ways of thinking about thought and its place in the
world. In their time and place, the mere demand that public discourse
be perspicuous, in particular, that reasoning be valid and premises
true--a demand implicit in their general ideal of
reason--placed them in the middle of crucial socio-political
struggles. Some members and sympathisers of the Circle also actively
opposed the then increasingly popular *volkisch*
supra-individual holism in social science as a dangerous intellectual
aberration. Not only did such ideas support racism and fascism in
politics, but such ideas themselves were supported only by radically
mistaken arguments concerning the nature and explanation of organic
and unorganic matter. So the first thing that made all of the Vienna
Circle philosophies politically relevant was the contingent fact that
in their day much political discourse exhibited striking epistemic
deficits. That some of the members of the Circle went, without logical
blunders, still further by arguing that socio-political considerations
can play a legitimate role in some instances of theory choice due to
underdetermination is yet another matter. This particular issue will
not be pursued further here (see references at the end of section 2.1
above), nor the general topic of the Circle's embedding in
modernism and the discourse of modernity (see Putnam 1981b for a
reductionist, Galison 1990 for a foundationalist, Uebel 1996 for a
constructivist reading of their modernism, Dahms 2004 for an account
of personal relations with representatives of modernism in art and
architecture).


## 3. Selected Doctrines and their Criticisms



Given only the outlines of Vienna Circle philosophy, its controversial
character is evident. The boldness of its claims made it attractive
but that boldness also seemed to be its undoing. Turning to the
questions of how far and, if at all, which forms of Vienna Circle
philosophy stand up to some common criticisms, both the synchronic
variations and the diachronic trajectories of its variants must be
taken into account. This will be attempted in the sections below.



Before expectations are raised too high, however, it must also
remembered that in this article only the views of members of the
Vienna Circle can be discussed, even though the problematic issues
were pervasive in logical empiricism generally. (Compare the SEP article "Logical Empiricism"; for articles on
Reichenbach see, e.g, Spohn 1991 and Salmon and Wolters 1994,
Richardson 2005, 2006, and, for the Berlin Group as a whole, Milkov and Peckhaus 2013.) Moreover, here
the emphasis must lie on the main protagonists: Schlick, Carnap and
Neurath. (Neither Hahn or Frank, nor Waismann or Feigl, for instance,
can be discussed here as extensively as their work deserves; see,
e.g., Uebel 2005b, 2011b, McGuinness 2011, Haller 2003, respectively.)
What will be noted, however, is that Vienna Circle philosophy was by
no means identical with the post-World War II logical empiricism that
has come to be known as the "received view" of scientific
theories, even though it would be hard to imagine the latter without
the former. (For a systematic if schematic critical discussion of the
received view, see Suppe 1977, for a partial defense Mormann
2007a.)



To deepen the somewhat cursory overview of Vienna Circle philosophy
given above, we now turn to the discussion of the following issues:
first, the viability of the conceptions of empirical significance
employed by the Vienna Circle in its classical period; second, its uses of
the analytic-synthetic distinction; third, its supposedly reductionist
designs and foundationalist ambitions for philosophy; fourth, its
stances in the debate about realism or anti-realism with regard to the
theoretical terms in science; fifth, Carnap's later ideas in
response to some of the problems encountered; sixth, the issue of the
status of the meaning criterion itself (variably referred to also as "criterion of significance" or "criterion of empirical significance") and of the point of their
critique of metaphysics; seventh, the Vienna Circle's attitude
towards history and of their own place in the history of
philosophy.



These topics have been chosen for the light their investigation throws
on the Circle's own agendas and the reception of its doctrines
amongst philosophers at large, as well as for the relative ease with
which their discussion allows its development and legacy to be
charted. There can be little doubt about the enormous impact that the
members of the Vienna Circle had on the development of
twentieth-century philosophy. What is less clear is whether any of its
distinctive doctrines are left standing once the dust of their
discussion has settled or whether those of its teachings that were
deemed defensible merged seamlessly into the broad church that
analytic philosophy has become (and, if so, what those surviving
doctrines and teachings may be).



It must be noted, then, that the topics chosen for this article do not
exhaust the issues concerning which the members of the Vienna Circle
made significant contributions (which continue to stimulate work in
the history of philosophy of science). Important topics like that of
the theory and practice of unified science, of the nature of the
empirical basis of science (the so-called protocol-sentence debate)
and of the general structure of the theories of individual sciences
can only be touched upon selectively. Likewise, while the general
topic of ethical non-cognitivism receives only passing mentions, the
Circle's varied approaches to value theory cannot be discussed
here (for an overview see Rutte 1986, for detailed analyses see Siegetsleitner 2014). Other matters, like the
contributions made by Vienna Circle members to the development of
probability theory and inductive logic, the philosophy of logic and
mathematics (apart from the guiding ideas of Carnap) and to the
philosophy of individual empirical sciences (physics, biology,
psychology, social science), cannot be discussed at all (see Creath
and Friedman 2007 and Richardson and Uebel 2007 for relevant essays with further references).
But it may be noted that with his "logic of science"
Carnap counts among the pioneers of what nowadays is called
"formal epistemology".


### 3.1 Verificationism and the Critique of Metaphysics



Not surprisingly, it was the Circle's rejection of metaphysics
by means of their seemingly devastating criterion of cognitive
significance that attracted immediate opposition. (That they did not
deny all meaning to statements thus ruled out of court was freely
admitted from early on, but this "expressive" surplus was
considered secondary to so-called "cognitive" meaning and
discountable in science (see Carnap 1928b, 1932a).) Notwithstanding
the metaphysicans' thunder, however, the most telling criticisms
of the criterion came from within the Circle or broadly sympathetic
philosophers. When it was protested that failure to meet an empiricist
criterion of significance did not make philosophical statements
meaningless, members of the Circle simply asked for an account of what
this non-empirical and presumably non-emotive meaning consisted in and
typically received no convincing answer. The weakness of their
position was rather that their own criterion of empirical significance
seemed to resist an acceptable formal characterization.



To start with, it must be noted that long before the verification
principle proper entered the Circle's discourse in the late 1920s,
the thought expressed by Mach's dictum that "where neither
confirmation nor refutation is possible, science is not
concerned" (1883 [1960, 587]) was accepted as a basic precept of
critical reflection about science. Responsiveness to evidence for and
against a claim was the hallmark of scientific discourse.
(Particularly the group Frank-Hahn-Neurath, who formed part of a
pre-World War I discussion group (Frank 1941, 1949a) sometimes called
the "First Vienna Circle" (Haller 1985, Uebel 2003), can
be presumed to be familiar with Mach's criterion.) Beyond this,
still in the 1920s, Schlick (1926) convicted metaphysics for falsely
trying to express as logically structured cognition what is but the
inexpressible qualitative content of experience. Already then,
however, Carnap (1928b, SS7) edged towards a formal criterion by
requiring empirically significant statements to be such that
experiential support for them or for their negation is at least
conceivable. Meaningfulness meant the possession of "factual
content" which could not, on pain of rendering many scientific
hypotheses meaningless, be reduced to actual testability. Instead, the
empirical significance of a statement had to be conceived of as
possession of the potential to receive direct or indirect experiential
support (via deductive or inductive reasoning).



In 1930, considerations of this sort appeared to receive a
considerable boost due to Waismann's reports of
Wittgenstein's meetings with him and Schlick. Wittgenstein had
discussed the thesis "The sense of a proposition is [the method of] its
verification" in conversations with Schlick and Waismann on 22
December 1929 and 2 January 1930 (see Waismann 1967 [1979, 47 and 79]) and Waismann elaborated it in his "Theses" which were presented to the Circle as
Wittgenstein's considered views. While Wittgenstein appears to have
thought of his dictum primarily as a constitutive principle of meaning, in the Circle it was put to work mainly as a demarcation criterion against metaphysics. Whether it was always noted that Wittgenstein's thesis and the criterion of cognitive significance must be distinguished (the former entails the latter, but not vice versa) may be doubted, but striking differences emerged all the same. Like Carnap's criterion of significance of 1928, the version of the criterion which followed from Wittgenstein's dictum also allowed for
verifiability in principle (and did not demand actual
verifiability): like Carnap's notion of experiential support, it worked with the mere conceivability of verifiability. Yet Wittgenstein's criterion required conclusive verifiability which Carnap's did not. (The demand for conclusive verifiability was discussed in the meetings
with Wittgenstein.) By 1931, however, it had become clear to some that
this would not do. What Carnap later called the "liberalization
of empiricism" was underway and different camps became
discernible within the Circle. It was over this issue that the
so-called "left wing" with Carnap, Hahn, Frank and Neurath
first distinguished itself from the "more conservative
wing" around Schlick. (See Carnap 1936-37, 422 and 1963a,
SS9. Carnap 1936-37, 37n dated the opposition to strict
verificationism to "about 1931".)



In the first place, this liberalization meant the accommodation of
universally quantified statements and the return, as it were, to
salient aspects of Carnap's 1928 conception. Everybody had noted
that Wittgenstein's criterion rendered
universally quantified statements meaningless. Schlick (1931) thus
followed Wittgenstein's own suggestion to treat "hypotheses" instead as
representing rules for the formation of verifiable singular
statements. (His abandonment of conclusive verifiability is indicated
only in Schlick 1936a.) By contrast, Hahn (1933, drawn from lectures
in 1932) pointed out that hypotheses should be counted as properly
meaningful as well and that the criterion be weakened to allow for
less than conclusive verifiability. But other elements played into
this liberalization as well. One that began to do so soon was the
recognition of the problem of the irreducibility of disposition terms
to observation terms (more on this presently). A third element was
that disagreement arose as to whether the in-principle verifiability
or support turned on what was merely logically possible or on what was
nomologically possible, as a matter of physical law etc. A fourth
element, finally, was that differences emerged as to whether the
criterion of significance was to apply to all languages or whether it
was to apply primarily to constructed, formal languages. Schlick
retained the focus on logical possibility and natural languages
throughout, but Carnap had firmly settled his focus on nomological
possibility and constructed languages by the mid-thirties. Concerned
with natural language, Schlick (1932, 1936a) deemed all statements
meaningful for which it was logically possible to conceive of a
procedure of verification; concerned with constructed languages only,
Carnap (1936-37) deemed meaningful only statements for whom it
was nomologically possible to conceive of a procedure of confirmation
of disconfirmation.



Many of these issues were openly discussed at the Paris congress in
1935. Already in 1932 Carnap had sought to sharpen his previous
criterion by stipulating that those statements were meaningful that
were syntactically well-formed and whose non-logical terms were
reducible to terms occurring in the basic observational evidence
statements of science. While Carnap's focus on the reduction of
descriptive terms allows for the conclusive verification of some
statements, it must be noted that his criterion also allowed
universally quantified statements to be meaningful in general, provided they were
syntactically and terminologically correct (1932a, SS2). It was
not until one of his Paris addresses, however, that Carnap officially
declared the criterion of cognitive significance to be mere confirmability.
Carnap's new criterion required neither verification nor
falsification but only partial testability so as now to include not
only universal statements but also the disposition statements of
science (see Carnap 1936-37; the English translation of the
original Paris address (1936a [1949]) combines it with extraneous
material). These disposition terms were thought to be linked to
observation statements by a variety of reduction postulates or longer
reduction chains, all of which provided only partial definitions
(despite their name they provided no eliminative reductions). Though
plausible initially, the device of introducing non-observational terms
in this way gave rise to a number of difficulties which impugned the
supposedly clear distinctions between logical and empirical matters
and analytic and synthetic statements (Hempel 1951, 1963).
Independently, Carnap himself (1939) soon gave up the hope that all
theoretical terms of science could be related to an observational base
by such reduction chains. This admission raised a serious problem for
the formulation of a criterion of cognitive significance: how was one to rule out
unwanted metaphysical claims while admitting as significant highly
abstract scientific claims?



Consider that Carnap (1939, 1956b) admitted as legitimate theoretical
terms that are implicitly defined in calculi that are
only partially interpreted by correspondence rules between
some select calculus terms and expressions belonging to an
observational language (via non-eliminative reductions). The problem
was that mere confirmability was simply too weak a criterion
to rule out some putative metaphysical claims. Moreover, this problem
arose for both the statement-based approach to the criterion (taken by
Carnap in 1928, by Wittgenstein in 1929/30, and by Ayer both in the
first (1936) and the second editions (1946) of *Language Truth and
Logic*) and for the term-based approach (taken by Carnap since
1932). For the former approach, the problem was that the empirical
legitimacy of statements obtained via indirect testing also
transferred to any expressions that could be truth-functionally
conjoined to them (for instance, by the rule of
'or'-introduction). Statements thus became empirically
significant, however vacuous they had been on their own. For the
term-based approach, the problem was that, given the non-eliminability
of dispositional and theoretical terms, empirical significance was no
longer ascribable to individual expressions in isolation but became a
holistic affair, with little guarantee in turn for the empiricist
legitimacy of all the terms now involved.



For most critics (even within the ranks of logical empiricism), the
problem of ruling out metaphysical statements while retaining the
terms of high theory remained unsolved. By 1950, in response to the
troubles of Ayer's two attempts to account for the indirect
testing of theoretical statements via their consequences, Hempel
conceded that it was "useless to continue to search for an
adequate criterion of testability in terms of deductive relationships
to observation sentences" (1950 [1959, 116]). The following
year, Hempel also abandoned the idea of using, as a criterion of
empirical significance, Carnap's method of translatability into
an antecedently determined empirical language consisting only of
observational non-logical vocabulary. Precisely because it was
suitably liberalized to allow abstract scientific theories with merely
partial interpretations, its anti-metaphysical edge was blunted: it
allowed for combination with "some set of metaphysical
propositions, even if the latter have no empirical interpretation at
all" (1951, 70). Hempel drew the holistic conclusion that the
units of empirical significance were entire theories and that the
measure of empirical significance itself was multi-criterial and,
moreover, allowed for degrees of significance. To many, this amounted
to the demise of the Circle's anti-metaphysical campaign. By
contrast, Feigl's reaction (1956) was to reduce the ambition of
the criterion of significance to the mere provision of necessary
conditions.



Some further work was undertaken on rescuing and, again, debunking a
version of the statement-based criterion, but mostly not by (former) members
of the Vienna Circle. However, in response to the problem of how to
formulate a meaning criterion that suitably distinguished between
empirically significant and insignificant non-observational terms,
Carnap proposed a new solution in 1956. We
will return to discuss it separately (see section 3.5 below); for
now we need only note that these proposals were highly technical and
applied only to axiomatized theories in formal languages. They too,
however, found not much favor amongst philosophers. Yet whatever the
problems that may or may not beset them, it would seem that far more
general philosophical considerations contributed to the disappearance
of the problem of the criterion of cognitive significance from most philosophical
discussions since the early 1960s (other than as an example of
mistaken positivism). These include the increasing opposition to the
distinctions between analytic and synthetic statements and
observational and theoretical terms as well as a general sense of
dissatisfaction with Carnap's approach to philosophy which began
to seem both too formalist in execution and too deflationary in
ambition. The entire philosophical program of which the search for a
precise criterion of empirical significance was a part had begun to
fall out of favor (and with it technical discussions about the
criterion's latest version).



The widely perceived collapse of the classical Viennese project to
find in an empiricist meaning criterion a demarcation criterion
against metaphysics--we reserve judgement about Carnap's
last two proposals here--can be interpreted in a variety of ways.
It strongly suggests that cognitive significance cannot be reduced to
what is directly observable, whether that be interpreted in
phenomenalist or intersubjective, physicalist terms. In that important
but somewhat subsidiary sense, the collapse spelt the failure of many
of the reductivist projects typically ascribed to Viennese
neopositivism (but see section 3.3 below). Beyond that, what actually
had failed was the attempt to characterize for natural languages the
class of cognitively significant propositions by recursive definitions
in purely logical terms, either by relations of deducibility or
translatability. What failed, in other words, was the attempt to apply
a general conception of philosophical analysis as purely formal,
pursued also in other areas, to the problem of characterizing
meaningfulness.



This general conception can be considered formalist in several senses.
It was formalist, first, in demanding the analysis of the meaning of
concepts and propositions in terms of logically necessary and
sufficient conditions: it was precise and brooked no exceptions. And
it was formalist, second, in demanding that such analyses be given
solely in terms of the logical relations of these concepts and
propositions to other concepts and propositions: it used the tools of
formal logic. There is also a third sense that is, however, applicable
predominantly to the philosophical project in Carnap's hands, in
that it was formalist since it concentrated on the analysis of
contested concepts via their explication in formal languages.
(Discussion of its viability must be deferred until sections 3.5 and
3.6 below, since what's at issue currently is only the formalist
project as applied to concepts in natural language.) The question
arises whether all Vienna Circle philosophers concerned with empirical
significance in natural language were equally affected, for the
collapse of the formalist project may leave as yet untouched other
ways of sustaining the objection that metaphysics is, in some relevant
sense, cognitively insignificant. (Such philosophers in turn would
have to answer the charge, of course, that only the formalist project
of showing metaphysics strictly meaningless rendered the Viennese
anti-metaphysics distinctive.)



Even though the formalist project became identified with mainstream
logical empiricism generally (consider its prominence in confirmation
theory and in the theory of explanation), it was not universally
subscribed to in the Vienna Circle itself. In different ways, neither
Schlick nor Neurath or Frank adhered to it. As noted in the overview
above, Schlick's attempts to exhibit natural language meaning
abjured efforts to characterize it in explicitly formal terms, even
though he accepted the demand for necessary and sufficient conditions
of significance. In the end, moreover, Schlick turned away from his
colleagues' search for a criterion of empirical significance. In
allowing talk of life after death as meaningful (1936a), for the very
reason that what speaks against it is only the empirical impossibility
of verifying such talk, Schlick's final criterion clearly left
empiricist strictures behind.



By contrast, Neurath and Frank kept their focus on empirical
significance. While they rarely discussed these matters explicitly,
their writings give the impression that Neurath and Frank chose to
adopt (if not retain) a contextual, exemplar-based approach to
characterizing the criterion of meaninglessness and so decided to
forego the enumeration of necessary and sufficient conditions.
Mach's precept cited earlier is an example of such a pragmatic
approach, as is, it should be noted, Peirce's criterion of
significance, endorsed by Quine (1969), which claims that significance
consists in making a discernible difference whether a proposition is
likely to be true or false. Mach's pragmatic approach had been
championed already before verificationism proper by Neurath, Frank and
Hahn who became, like Carnap, early opponents of conclusive
verifiability. (Indeed, it is doubtful whether Neurath's radical
fallibilism, most clearly expressed already in 1913, ever wavered.)
This pragmatic understanding found clear expression in Neurath's
adoption (1935a, 1938) of K. Reach's formulation of metaphysical
statements as "isolated" ones, as statements that do not
derive from and hold no consequences for those statements that we do
accept on the basis of empirical evidence or for logical reasons.
(Hempel's dismissal, in 1951, of this pragmatic indicator
presupposes the desiderata of the formalist project.) Finally, there
is Frank's suggestion (1963), coupled with his longstanding
advice to combine logical empiricism with pragmatism, that
Carnap's purely logical critique of metaphysics in (1932a) was
bound to remain ineffective as long as the actual use of metaphysics
remained unexamined. It would be worth investigating whether--if
the critique of the alleged reductionist ambitions of their philosophy
could also be deflected (see section 3.3 below)--the impetus of
the anti-verificationist critique can be absorbed by those with a
pragmatic approach to the demarcation against metaphysics. Much as
with Quine's Peirce, such a criterion rules out as without
interest for epistemic activity all concepts and propositions whose
truth or falsity make no appreciable difference to the sets of
concepts and propositions we do accept already.



An entirely different moral was drawn by Reichenbach (1938) and
thinkers indebted to his probabilistic conception of meaning and his
probabilistic version of verificationism, which escaped the criticisms
surveyed above by vagaries of its own. Such theorists perceive the
failure of the formalist model to accommodate the empirical
significance of theoretical terms to stem from its so-called deductive
chauvinism. In place of the exclusive reliance on the
hypothetical-deductive method these theorists employ non-demonstrative
analogical and causal inductive reasoning to ground theoretical
statements empirically. Like Salmon, these theorists adopt a form of
"non-linguistic empiricism" which they sharply
differentiate from the empiricism of the Vienna Circle (Salmon 1985,
2003 and Parrini 1998).



Now against both the pragmatic and the post-linguistic responses to
the perceived failure of the attempt to provide a precise formal
criterion of significance serious worries can be raised. Thus it must
be asked whether without a precise way of determining when a statement
'makes an appreciable difference', criticism of
metaphysics based on such a criterion may be not be considered as a
biased dismissal rather than a demonstration of fact and so fall short
of what is needed. Likewise in the case of the anti-deductivist
response, it must be noted that a criterion based on analogical
reasoning will only be as effective as the strength of the analogy
which can always be criticized as inapt (and similarly for appeals to
causal reasoning). The very point of exact philosophy in a scientific
spirit--for many the very point of Vienna Circle philosophy
itself--seems threatened by such maneuvres. Acquiescence in the
perceived failure of the proposed criteria of significance thus comes
with a price: if not that of abandoning Vienna Circle philosophy
altogether, then at least that of formulating an alternative
understanding to how some of its ambitions ought to be understood.
(Recent reconstructive work on Carnap, Neurath and Frank may be
regarded in this light.)



A still different response--but one emblematic for the
philosophical public at large--is that of another of
Reichenbach's former students, Putnam, who came to reject
the anti-metaphysical project that powered verificationism in its
entirety. Repeatedly in his later years, Putnam called for a
refashioning of analytic philosophy as such, providing, as it were, a
philosophically conservative counterweight to Rorty's turn to
postmodernism. Putnam's reasons (the alleged self-refutation of
the meaning criterion) are still different from those surveyed above
and will be discussed when we return to reconsider the very point of
the Circle's campaign against metaphysics (see section 3.6
below).


### 3.2 The Analytic/Synthetic Distinction and the Relative *A Priori*



Whether the verificationist agenda was pursued in a formalist or
pragmatic vein, however, all members shared the belief that meaningful
statements divided exclusively into analytic and synthetic statements
which, when asserted, were strictly matched with *a priori* and
*a posteriori* reasoning for their support. The Vienna Circle
wielded this pairing of epistemic and semantic notions as a weapon not
only against the substantive *a priori* of the Schoolmen but
also against Kant's synthetic *a priori*. Moreover, their
notion of analyticity comprized both logical and mathematical truths,
thereby extending Wittgenstein's understanding of the former as
"tautological" in support of a broadly logicist
program.



It is well known that this central component of the Vienna
Circle's arsenal, the analytic/synthetic distinction, came under
sharp criticism from Quine in his "Two Dogmas of
Empiricism" (1951a), less so that the criticism can only be
sustained by relying on objections of a type first published by
Tarski. The argument is more complex, but here is a very rough sketch.
So as to discard the analytic/synthetic distinction as an unwarranted
dogma, Quine in "Two Dogmas" argued for the in-principle
revisability of all knowledge claims and criticised the impossibility
of defining analyticity in a non-circular fashion. The first argument
tells against the apodictic *a priori* of old (the eternal
conceptual verities), but, as we shall see, it is unclear whether it
tells against at least some of the notions of the *a priori*
held in the Vienna Circle. The second argument presupposes a
commitment to extensionalism that likewise can be argued not to have
been shared by all in the Circle. By contrast, Tarski had merely
observed that, at a still more fundamental level, he knew of no basis
for a sharp distinction between logical and non-logical terms. (For
relevant primary source materials see also Quine 1935, 1951b, 1963,
Carnap 1950, 1955, 1963b, their correspondence and related previously
unpublished lectures and writings in Creath 1990, the memoir Quine
1991, and Tarski 1936.)



The central role on the Vienna Circle's side in this discussion
falls to Carnap and the reorientation of philosophy he sought to
effect in *Logical Syntax* (1934/37). It was the notion of the
merely relative and therefore non-apodictic *a priori* that
deeply conditioned his notion of analyticity and allowed him to
sidestep Quine's fallibilist argument in a most instructive
fashion. In doing so Carnap built on an idea behind
Reichenbach's early attempt (1920) to comprehend the general
theory of relativity by means of the notion of a merely constitutive
*a priori*. Now Schlick had objected to the residual idealism
of this proposal (see Oberdan 2009) and prefered talk of conventions
instead and Reichenbach soon followed him in this (see Coffa 1991, Ch.
10). Carnap too did not speak of the relative *a priori* as
such (in returning to this terminology present discussions follow
Friedman 1994), but his pluralism of logico-linguistic frameworks
furnishes precisely that.



First consider Schlick as a contrast class. Schlick (1934) appeared to
show little awareness of the language-relativity of the
analytic/synthetic distinction and spoke of analytic truths as
conceptual necessities that can be conclusively surveyed. This would
suggest that Schlick rejected Kant's apodictic synthetic *a
priori* but not the apodicity of analytic statements. Clearly, if
that were so, Quine's argument from universal fallibilism would
find a target here. Matters are not quite so clear-cut, however.
Schlick had long accepted the doctrine of semantic conventionalism
that the same facts could be captured by different conceptual systems
(1915): this would suggest that his analytic truths were conventions that were
framework-relative and as such necessary only in the very frameworks
they helped to constitute. Yet Schlick did not countenance
the possibility of incommensurable conceptual frameworks:
any fact was potentially expressible in any framework (1936b). As a
result, Schlick did not accept the possibility that after the adoption
of a new framework the analytic truths of the old one may be no longer
assertable, that they could be discarded as no longer applicable even
in translation, as it were. Herein lay a point that Quine's
argument could exploit: Schlick's analytic truths remained
unassailable despite their language-relativity.



Now Carnap, under the banner of the principle of logical tolerance
(1934/37, SS17), abandoned the idea of the one universal logic
which had informed Frege, Russell and Wittgenstein before him.
Instead, he recognized a plurality of logics and languages whose
consistency was an objective matter even though axioms and logical
rules were fixed entirely by convention. Already due to this logical
pluralism, the framework-relativity of analytic statements went deeper
for Carnap than it did for Schlick. But Carnap also accepted the
possibility of incommensurability between seemingly similar
descriptive terms and between entire conceptual systems (1936a).
Accepting the analytic truths of the framework of our best physical
theory may thus be incompatible with accepting those of an earlier
one, even if the same logic is employed in both. Carnapian
analyticities do not therefore express propositions that we hold to be
true unconditionally, but only propositions true relative to their own
framework: they are no longer held to be
potentially translatable across all frameworks. Quine's charge of
universal revisability (which itself needs some modification; see
Putnam 1978) thus misses its mark against them. (Quine, of course, also
rejected Carnap's ultimately intensionalist accommodation of radical
fallibilism via the notion of language change.)



Concerning the criticism of the circular nature of the definition of
analyticity, Carnap responded that it pertained primarily to the idea
of analyticity in natural language whereas he was interested in
"explications" as provided by the logic of science (or
better, a logic of science, since there existed no unique logic of
science for Carnap). Explications are reconstructions in a formal
language of selected aspects of complex terms that should not be
expected to model the original in all respects (1950b, Ch.1).
Moreover, Carnap held that explication of the notion of analyticity in
formal languages yielded the kind of precision that rendered the
complaint of circularity irrelevant: vague intuitions of meaning were
no longer relied upon. Those propositions of a given language were
analytic that followed from its axioms and, once the syntactic
limitations of the *Logical Syntax* period had been left
behind, from its definitions and meaning postulates, by application of
its rules: no ambiguity obtained.



So it may appear that the notion of analyticity is easily delimitable
in Carnap's explicational approach: analytic propositions would
be those that constitute a logico-linguistic framework. But
complications arose from the fact that, on Carnap's
understanding, not all propositions defining a logico-linguistic
framework need be analytic ones (1934/37, SS51). It was possible
for a framework to consist not only of L-rules, whose entirety
determines the notion of logical consequence, but also of P-rules,
which represent presumed physical laws. So let analytic propositions
be those framework propositions whose negations are
self-contradictory. Here a problem arose once the syntactic
constraints were dropped by Carnap after *Logical Syntax* so as
to allow semantic reasoning and the introduction of so-called meaning
postulates: now the class of analytic propositions was widened to
include not only logical and mathematical truths but also those
obtained by substitution of semantically equivalent expressions. How
was one now to explicate the idea that there can be non-analytic
framework propositions (whose negations are not self-contradictory)?
Consider that for opponents like Quine, responding that the negations
of non-analytic framework propositions do not contradict meaning
postulates, was merely to dress up a presupposed notion of meaning in
pseudo-formal garb: while it provided what looked like formal
criteria, Carnap's method did not leave the circle of
intensional notions behind and so seemed to beg the question. Meaning
postulates (Carnap 1952), after all, could only be identified by
appearing on a list headed "meaning postulates" (as Quine
added in reprints of 1951a).



Here one must note that in *Logical Syntax*, Carnap also
modified the thesis of extensionality he had previously defended
alongside Russell and Wittgenstein: now it merely claimed the
possibility of purely extensional languages and no longer demanded
that intensional languages be reduced to them (*ibid.*,
SS67). Of course, the mere claim that the language of science can
be extensional still proves troublesome enough, given that in such a
language a distinction between laws and accidentally true universal
propositions cannot be drawn (the notion of a counterfactual
conditional, needed to distinguish the former, is an intensional one).
Even so, this opening of Carnap's towards intensionalism already
at the height of his syntacticism--to say nothing of his explicit
intensionalism in *Meaning and Necessity* (1947)--seems
enough to thwart Quine's second complaint in "Two
Dogmas". Carnap did not share Quine's extensionalist
agenda, so the need to break out of the circle of intensional notions
once these were clearly defined in his formal languages did not apply.
That theirs were in fact different empiricist research programmes was
insufficiently stressed, it would appear, by Quine and Quinean critics
of Carnap (as noted pointedly by Stein 1992; cf. Ricketts 1982, 2003, Creath 1991, 2004,
Richardson 1997).



To sustain his critique, Quine had to revive his and Tarski's
early doubts about Carnap's methodological apparatus and dig
even deeper. (Tarski also shared Quine's misgivings about
analyticity when they discussed these issues with Carnap at Harvard;
see Mancosu 2005, Frost-Arnold 2013.) Their scepticism found its
target in Carnap's ingenious measures in *Logical Syntax*
taken to preserve the thesis that mathematics is analytic from the
ravages of Godel's incompleteness theorems. Godel
proved that every formal system strong enough to represent number
theory contains a formula that is true but neither itself or its
negation is provable in that system; such formulae--known since
as Godel sentences--are provable in a still stronger system
which, however, also contains a formula of its own that is true but
not provable in it (and neither is its negation). Commonly,
Godel's proof is taken to have undermined the thesis of the
analyticity of arithmetic. (For discussions of this challenge to
Carnap's logical syntax project, see Friedman 1988, 1999a, 2009,
Goldfarb and Ricketts 1992, Richardson 1994, Awodey and Carus 2003,
2004.) Carnap responded by stating that arithmetic demands an infinite
sequence of ever richer languages and by declaring analytic statements
to be provable by non-finite reasoning (1934/37, SS60a-d). This
looked like fitting the bill on purely technical grounds, but it is
questionable whether such reasoning may still count as syntactic.
Nowadays, it is computational effectiveness that is taken to
distinguish purely formal from non-formal, material reasoning.
(Carnap's move highlights the tension within *Logical
Syntax* between formal and crypto-semantic reasoning: that the rigid
syntacticism officially advertised there was at the same time
undermined as its failings were being compensated--illegitimately so
by official standards, e.g., by considering translatability a
syntactic notion--points ahead to his acceptance of semantics in 1935, only one
year after the publication of *Logical Syntax* and contrary to
his disparagement of the notion of synthetic truth there. For a discussion of Carnap's moves, see Coffa
1978, Ricketts 1996, Goldfarb 1997, Creath 1996, 1999.) It is no
criticism that Carnap's reconstruction of arithmetic was not
standard logicism, but that Carnap unduly stretched the idea of formal
reasoning is. Was he saved by his shift to semantics?



Tarski (1936) granted the language-relativity of the reconstructed
notion of analyticity in *Logical Syntax*. He also did not
object that Carnap's procedure of circumventing the problem
which the Godel sentences presented to the thesis of the
analyticity of arithmetic was illegitimate. Tarski rather questioned
whether there were "objective reasons" for the sharp
distinction between logical and non-logical terms and he pointed out
that Carnap's distinction between the logical and the empirical
was not a hard and fast one. Since noting that the distinction between
logical and non-logical was not a sharp one and arguing that no
principled distinction could be upheld between them are two quite
different reactions, however, Tarski's point on its own does not
fully support the Quinean critique. Quine's conclusion (1940,
SS60) that the notion of logical truth itself is
"informal" rather reflects the moral that he drew from
Tarski's observation. It appears that what motivated him (after
a nominalistic interlude in the 1940s) to develop his naturalistic alternative to
Carnap's conception of philosophy was his considered rejection
of Carnap's accommodation of the thesis that arithmetic is
analytic to Godel's result.



Different strands of Quine's criticism of the analytic/synthetic
distinction must thus be distinguished. While Quine's criticisms
in "Two Dogmas" on their own clearly did not undermine all
forms of the distinction that were defended in the Vienna
Circle--Carnap's reconstructions of the notion of
analyticity did not express unconditionally necessary and unrevisable
propositions--they do gain in plausibility even against
Carnap's once it is recognized that the deepest ground of
contestation lies elsewhere: not in the notion of analyticity widely
understood but in that of logical truth narrowly understood. Read in
this way, Quine can be seen to argue that the notion of L-consequence
as explication of analytic truth--as opposed to P-consequence as
non-analytic, mere framework entailments--traded not only on the
idea of non-finitary notions of proof but also on a distinction of
logical from descriptive expressions that itself only proceeded on the
basis of a finite enumeration of the former (compare Carnap 1934/37,
SSSS51-52). (This deficit was not repaired in
Carnap's later work either; see Awodey 2007.) What Quine
criticized was precisely the fact that Carnap could ground the
distinction between logical and non-logical terms no deeper than by
the enumeration of the former in a given framework: was the
distinction therefore not quite arbitrary? 



Quine's direct arguments against the distinction between logical
and empirical truth (1963) have been found to beg the question against
Carnap and his way of conceiving of philosophy (Creath 2003). This way
of responding to Quine's objection requires us to specify still
more precisely just what Carnap thought he was doing when he employed
the distinction between analytic and synthetic propositions. To be
sure, in (1955) he gave broadly behavioural criteria for when meaning
ascriptions could be deemed accepted in linguistic practice, but he also noted that this was not a general requirement for the
acceptability of explicatory discourse. To repeat, explications did
not seek to model natural language concepts in their tension-filled
vividness, but to make proposals for future use and to extract and
systematize certain aspects for constructive purposes. Thus Carnap
clarified (1963b, SS32) that he regarded the distinction between
analytic and synthetic statements--just like the distinction
between descriptive or factual and prescriptive or evaluative
statements--not as descriptive of natural language practices, but
as a constructive tool for logico-linguistic analysis and theory
construction. It is difficult to overstress the significance of this
stance of Carnap's for the evaluation of his version of the
philosophical project of the Vienna Circle. Carnap's
understanding of philosophy has thus been aptly described as the
"science of possibilities" (Mormann 2000). 



As Carnap understood the analytic/synthetic distinction, it was a
distinction drawn by a logician to enable greater theoretical
systematicity in the reconstructive understanding of a given symbol
system, typically a fragment of a historically developed one. That
fully determinative objective criteria of what to regard as a logical
and what as a non-logical term cannot be assumed to be pre-given does
not then in and of itself invalidate the use of that distinction by
Carnap. On the contrary, it has been convincingly argued that Carnap
himself did not hold to a notion of what is a factual and what is a
formal expression or statement that was independent of the
specification of the language in question (Ricketts 1994). The
ultimate ungroundedness of his basic semantic explicatory categories,
this suggests instead, was a fact that his own theories fully
recognized and consciously exploited. (Somewhat analogously, that we
cannot define science independently of the practice of scientists of
"our culture" was admitted by Neurath 1932a, Carnap 1932d
and Hempel 1935, much to the exasperation of Zilsel 1932 and Schlick
1935a.)



It remained open for Carnap then to declare his notion of analyticity
to be only operationally defined for constructed languages and to let
that notion be judged entirely in terms of its utility for
meta-theoretical reflection. Just on that account, however, a last
hurdle remains: finding a suitable criterion of significance for
theoretical terms that allows the distinction between analytic and
synthetic statements to be drawn in the non-observational, theoretical
languages of science. (This was a problem ever since the
non-eliminative reducibility of disposition terms had been accepted
and one that still held for Carnap's 1956 criterion; see section
3.5 below). Only if that can be done, we must therefore add, can
Carnap claim his formalist explicationist project to emerge unscathed
from the criticisms of both Tarski and Quine.



An important related though independently pursued line of criticism
may be noted here. It finds its origin in Saunders Mac Lane's
review (1937) of Carnap's *Logical Syntax* and focusses
less on the analytic/synthetic distinction than on Carnap's
failure to give a formally correct definition of logic. It challenges
the ambition to have accounted for the formal sciences but declines to
embrace a naturalistic alternative. Further research along these lines
has suggested to some that by extending Carnap's approach and
framework it can be linked to attempts in category theory to provide
the missing definition (see Awodey 2012, 2017), while a different response to Mac Lane's as well as Quine's criticisms defends Carnap's inability, frankly admitted in (1942, 57) to define logical terms as such in full generality (Creath 2017).



None of the above considerations should lead one to deny, however,
that one can find understandings of the term "analytic" by
members of the Vienna Circle (like Schlick) that do fall victim to the
criticisms of Quine more easily. Nor should one discount the fact that
Carnap's logic of science emerges as wilfully ill-equipped to
deal with the problems that exercise the traditional metaphysics or
epistemologies that deal in analyticities. (Of course, unlike his
detractors, Carnap considered this to be a merit of his approach.)
Lastly, it must be noted that Carnap's intensionalist logic of
science holds out the promise of practical utility only for the price
of a pragmatic story that remains to be told. Of what nature are the
practical considerations and decisions that, as Carnap so freely
conceded (1950a), are called for when choosing logico-linguistic
frameworks? (Such conventional choices do not respond to truth or
falsity, but instead to whatever is taken to measure convenience.)
That Carnap rightly may have considered such pragmatic questions
beyond his own specific brief as a logician of science does not
obviate the need for an answer to the question itself. (Carus 2007
argues that in this broadly pragmatic dimension lies the very point of
Carnap's explicationism.) On this issue, too, it would have been
helpful if there had been more collaboration with Neurath and Frank,
who were sympathetic to Carnap's explication of analyticity but
did not refer to it much in their own, more practice-oriented
investigations (see section 3.6 below).


### 3.3 Reductionism and Foundationalism: Two Criticisms Partly Rebutted



As it happens, anti-verificationism has two aspects: opposition to
meaning reductionism and opposition to the formalist project. Turning
to the former, we must distinguish two forms of reductionism,
phenomenalist and physicalist reductionism. Phenomenalism holds
statements to be cognitively significant if they can be reduced to
statements about one's experience, be it outer (senses) or inner
(introspection). Physicalism holds statements to be cognitively
significant if they can be reduced or evidentially related to
statements about physical states of affairs. Here it must be noted not
only that the Vienna Circle is typically remembered in terms of the
apparently phenomenalist ambitions of Carnap's *Aufbau*
of 1928, but also that already by the early 1930s some form of
physicalism was favoured by some leading members including Carnap
(1932b) and that already in the *Aufbau* the possibility of a
different basis for a conceptual genealogy than the phenomenal one actually chosen had been indicated. Thus one
must not only ask about the reductionism in the *Aufbau* but
also consider just how reductivist in intent the physicalism was meant
to be.



Considerations can begin with an early critique that has given rise in
some quarters to a sharp distinction between Viennese logical
positivism and German logical empiricism, with the former accused of
reductionism and the latter praised for their anti-reductionism, a
distinction which falsely discounts the changing nature and variety of
Vienna Circle doctrines. Reichenbach's defense of empiricism
(1938) turned on the replacement of the criterion of strict
verifiability with one demanding only that the degree of probability
of meaningful statements be determinable. This involved opposition
also to demands for the eliminative reduction of non-observational to
observational statements: both phenomenalism and reductive physicalism
were viewed as untenable and a correspondentist realism was advanced
in their stead. Now it is true that of the members of the Vienna
Circle only Feigl ever showed sympathies for scientific realism, but
it is incorrect that all opposition to it in the Circle depended on
the naive semantics of early verificationism. Again, of course, some
Vienna Circle positions were liable to Reichenbach's
criticism.



Another misunderstanding to guard against is that the Vienna
Circle's ongoing concern with "foundational issues"
and the "foundations of science" does in itself betoken
foundationalism. (In the Vienna Circle's days, foundationalism
had it that the basic items of knowledge upon which all others
depended were independent of each other, concerned phenomenal states
of affairs and were infallible; nowadays, foundationalists drop
phenomenalism and infallibility.) Already the manifesto sought to make
clear the Circle's opposition when it claimed that "the
work of 'philosophic' or 'foundational'
investigations remains important in accord with the scientific world
conception. For the logical clarification of scientific concepts,
statements and methods liberates one from inhibiting prejudices.
Logical and epistemological analysis does not wish to set barriers to
scientific enquiry; on the contrary, analysis provides science with as
complete a range of formal possibilities as is possible, from which to
select what best fits each empirical finding (example: non-Euclidean
geometries and the theory of relativity)." (Carnap-Hahn-Neurath
1929 [1973, 316]) This passage can be read as an early articulation of
the project of a critical-constructivist meta-theory of science that
abjures a special authority of its own beyond that stemming from the
application of the methods of the empirical and formal sciences to
science itself, but instead remains open to what the actual practice
of these sciences demands.



How then can Vienna Circle philosophy be absolved of foundationalism? As
noted, it is the *Aufbau* (and echoes of it in the manifesto)
that invites the charge of phenomenalist reductionism. To begin with,
one must distinguish between the strategy of reductionism and the
ambition of foundationalism. Concerning the *Aufbau* it has
been argued that its strategy of reconstructing empirical knowledge
from the position of methodological solipsism (phenomenalism without
its ontological commitments and some of its epistemological ambitions)
is owed not to foundationalist aims but to the ease by which this
position seemed to allow the demonstration of the interlocking and
structural nature of our system of empirical concepts, a system that
exhibited unity and afforded objectivity, which was Carnap's
main concern. (See Friedman's path-breaking 1987 and 1992, and Richardson 1990, 1998, Ryckman
1991, Pincock 2002, 2005. For the wide variety of influences on the
*Aufbau* more generally, see Dambock 2016.) However, it is
hard to deny categorically that Carnap ever harbored foundationalist
ambitions. Not only did Carnap locate his *Aufbau* very close
to foundationalism in retrospect (1963a), but a passage in his (1930)
led Uebel (2007, Ch.6) to claim that around 1929/30 Carnap was motivated by
foundationalist principles and reinterpreted his own *Aufbau*
along these lines (around the same time that Wittgenstein
entertained a psychologistic reinterpretation of his own
*Tractatus* that was reported back to the Circle by Waismann).
To correct this foundationalist aberration was the task of the
Circle's subsequent protocol-sentence debate about the content,
form and status of the evidence statements of science.



This concession to the foundationalist misinterpretation of Vienna
Circle philosophies generally must not, however, be taken to tell
against the new reading of the *Aufbau* or the epistemologies
developed from 1930 onwards on the physicalist wing of the Circle. In fact, the *Aufbau* itself fails when it is read as
a foundationalist project, as it was by Quine (1951a) who pointed out
that no eliminative definition of the relation 'is at' was
provided (required for locating objects of consciousness in physical
space). Yet other failures of reduction were detected by Richardson (1998, Ch.3), further questioning the *Aufbau's* supposed foundationalist intent. Ultimately it was a still different failure of reduction that prompted Carnap to abandon as
mistaken reconstructions of the scientific language on the basis of
methodological solipsism (though not logical investigations of such languages for their own sake, as noted in his 1961a). Initially Carnap had not been prepared to draw this conclusion even though Neurath (1931b, 1932a) argued that such a type of
rational reconstruction traded on objectionable
counterfactual presuppositions (methodological solipsism did not
provide a correct description of the reasoning involved in cognitive
commerce with the world around us). At the time Carnap
merely conceded that it was more "convenient" to
reconstruct the language of science on a physicalistic basis (1932e). Only the failure of reducing dispositional predicates to observational ones convinced him to abandon the methodologically solipsist approach (1936-37, 464 and 10) and to adopt an exclusively physicalist basis for his reconstructions of the language of science from then on (a decision explicitly reaffirmed in 1963b). 
Carnap's initial reluctance to draw this conclusion is best interpreted, not as hankering after epistemological foundations, but as indicating the growing conviction that philosophical methodology had to be built on logical reasons and should not be "entangled with psychological
questions" (1934/37, SS72). Moreover, already Carnap's initial hope for a phenomenalist reduction in the *Aufbau* as well as his decision in (1932e) to loosen the methodologically solipsist claim on epistemology were motivated by logical considerations, the former by mistaken ideas in *Untersuchungen zur allgemeinen Axiomatik* (2000, unpublished at the time) and the latter partly as a consequence of Godel's advice on a faulty definition of analyticity in a draft of *Logical Syntax* (see Ricketts 2010 and Awodey and Carus 2007 respectively).



It could likewise be asked concerning physicalism whether it represented, on a different basis, the pursuit of a
foundationalist agenda. But that Carnap later in
(1936/37) called his non-eliminative definitions of disposition
terms "reduction sentences" already indicates that it was enough
for him to provide a basis for the applicability of these terms by
merely sufficient but not necessary conditions. Likewise,
Carnap's proposal (1939) to conceive of theoretical terms as
defined by implicit definition in a non-interpreted language, selected terms of which were, however, linked via non-eliminative
reductive chain to the observational language, suggests that what concerned him
primarily was the capture of indicator relations to sustain in
principle testability of statements containing the terms in question.
This is best understood as an attempt to preserve the empirical
applicability of the formal languages constructed for high-level theory, but
not as reductivism with regard to some foundational given.



By contrast, Neurath never advocated methodological solipsism. Consider that his
complex conception of the form of protocol statements (1932b)
explicated the concept of observational evidence in terms that
expressly reflected debts to empirical assumptions which called for
theoretical elaboration in turn. For unlike the logician of science
Carnap, who left it to psychology and brain science to determine more
precisely what the class observational predicates were that could
feature in protocol statements (1936/37), the empirically oriented
meta-theoretician of science Neurath was concerned to encompass and
comprehend the practical complexities of reliance on scientific
testimony: the different clauses (embeddings) of his proposed protocol
statements stand for conditions on the acceptance of such testimony
(see Uebel 2009). In addition, Neurath's theory of protocol
statements also makes clear that his understanding of physicalism did
not entail the eliminative reduction of the phenomenon of
intentionality but, like Carnap (1932c), merely sought its integration
into empiricist discourse.



Given these different emphases of their respective physicalisms,
mention must also be made of the significant differences between
Carnap's and Neurath's conceptions of unified science:
where the formalist Carnap once preferred a hierarchical ordering of
finitely axiomatized theoretical languages that allowed at least
partial cross-language definitions and derivations--these
requirements were liberalized over the years (1936b), (1938),
(1939)--the pragmatist Neurath opted from the start to demand
only the interconnectability of predictions made in the different
individual sciences (1935a), (1936c), (1944). (Metereology, botany and
sociology must be combinable to predict the consequences of a forest
fire, say, even though each may have its own autonomous theoretical
vocabulary.) Here too it must be remembered that, unlike Carnap,
Neurath only rarely addressed issues in the formal logic of science
but mainly concerned himself with the partly contextually fixed
pragmatics of science. (One exception is his 1935b, a coda to his
previous contributions to the socialist calculation debate with Ludwig
von Mises and others.) Not surprisingly, at times the priorities set
by Neurath for the pragmatics of science seemed to conflict with those
of Carnap's logic of science. (These tensions often were
palpable in the grand publication project undertaken by Carnap and
Neurath in conjunction with Morris, the International Encyclopedia of
the Unity of Science; see Reisch 2003.) That said, however, note that
Carnap's more hierarchical approach to the unity of science also
does not support the attribution of foundationalist ambitions.



But for a brief lapse around 1929/30 and perhaps in some pre-Vienna years, then,
Carnap fully represents the position of Vienna Circle
anti-foundationalism. In this he joined Neurath whose long-standing
anti-foundationalism is evident from his famous simile, first used in
1913, that likens scientists to sailors who have to repair their boat
without ever being able to pull into dry dock (1932b). Their positions
contrasted at least *prima facie* with that of Schlick (1934)
who explicitly defended the idea of foundations in the Circle's
protocol-sentence debate. Even Schlick conceded, however, that all
scientific statements were fallible ones, so his position on
foundationalism was by no means the traditional one. The point of his
"foundations" remained less than wholly clear and
different interpretation of it have been put forward (e.g., Oberdan 1998, Uebel 1996, 2020). (On the protocol
sentence debate as a whole, which included not only the debate between
Carnap and Neurath but also debates between the physicalists and Schlick and other occasional participants,
see, e.g., the differently centered accounts of Uebel 1992, 2007,
Oberdan 1993, Cirera 1994.) While all in the Circle thus recognized as
futile the attempt to restore certainty to scientific knowledge
claims, not all members embraced positions that rejected
foundationalism *tout court*. Clearly, however, attributing
foundationalist ambitions to the Circle as a whole constitutes a total
misunderstanding of its internal dynamics and historical development,
if it does not bespeak wilfull ignorance. At most, a foundationalist
faction around Schlick can be distinguished from the so-called left
wing whose members pioneered anti-foundationalism with regard to both
the empirical and formal sciences.


### 3.4 Scientific Theories, Theoretical Terms and the Problem of Realism



Yet even if it be conceded that the members of the Vienna Circle did
not harbour undue reductionist-foundationalist ambitions, the question
remains open whether they were able to deal with the complexities of
scientific theory building.



Here the prominent role of Schlick must be mentioned, whose
*General Theory of Knowledge* (1918, second edition 1925) was
one of the first publications by (future) members of the Vienna Circle
to introduce the so-called two-languages model of scientific theories.
According to this model, scientific theories comprised an
observational part formulated with observational predicates as
customarily interpreted, in which observations and experiential laws
were stated, and a theoretical part which consisted of theoretical
laws the terms of which were merely implicitly defined, namely, in
terms of the roles they played in the laws in which they figured. Both
parts were connected in virtue of a correlation that could be
established between selected terms of the theoretical part and
observational terms. In the second half of the 1920s, however,
Schlick's model, involving separate conceptual systems, was put
aside in favor of a more streamlined conception of scientific theories
along lines as suggested by the *Aufbau*. Clearly, however,
Schlick's model represents an early form of the conception of
scientific theories as uninterpreted calculi connected to observation
by potentially complicated correspondence rules that Carnap
reintroduced in (1939) and that became standard in the "received
view". (Another, albeit faint precursor was the idea contained
in a 1910 remark of Frank's pointing out the applicability of
Hilbert's method of implicit definition to the reconstruction
empirical scientific theories as conceived, also along the lines of
two distinct languages, by the French conventionalists Rey and Duhem;
see Uebel 2003.)



Even granted the model in outline, questions arise both concerning its
observational base as well as its theoretical superstructure. We
already discussed one aspect of the former topic, the issue of
protocols, in the previous section; let's here turn to the
latter topic. Talk of correspondence rules only masks the problem that
is raised by theoretical terms. One of the pressing issues concerns
their so-called surplus meaning over and above their observational
consequences. This issue is closely related to the problem of
scientific realism: are there truth-evaluatable matters of fact for
scientific theories beyond their empirical, observational adequacy?
Even though the moniker "neo-positivism" would seem to
prescribe an easy answer as to what the Vienna Circle's position
was, it must be noted that just as there is no consensus discernible
today there was none in the Circle beyond certain basics that left the
matter undecided.



All in the Vienna Circle followed Carnap's judgement in
*Pseudoproblems of Philosophy* (1928b) and Schlick's
contention in his response to Planck's renewal of anti-Machian
polemics (1932) that questions like that of the reality of the
external world were not well-formed ones but only constituted
pseudo-questions. While this left the observables of empirical reality
clearly in place, theoretical entities remained problematical: were
they really only computational fictions introduced for the ease with
which they they allowed complex predictive reasoning, as Frank (1932)
held? This hardly seems to do justice to the surplus meaning of
theoretical terms over and above their computational utility: theories
employing them seem to tell us about non-observable features of the
world. This indeed was Feigl's complaint (1950) in what must
count as the first of very few forays into "semantical
realism" (scientific realism by another word) by a former member
of the Vienna Circle--and one that was quickly opposed by
Frank's instrumentalist rejoinder (1950). Carnap sought to remain
aloof on this as on other ontological questions. So while in the
heyday of the Vienna Circle itself the issue had not yet come into
clear focus, by mid-century one could distinguish amongst its
surviving members both realists (Feigl) and anti-realists (Frank) as
well as ontological deflationists (Carnap).



Carnap's general recipe for avoiding undue commitments (while
pursuing his investigations of various language forms, including the
intensional ones Quine frowned upon) was given in terms of the
distinction between so-called internal and external questions (1950a).
Given the adoption of a logico-linguistic framework, we can state the
facts in accordance with what that framework allows us to say. Given
any of the languages of arithmetic, say, we can state as arithmetical
fact whatever we can prove in them; to say that there are
numbers, however, is at best to express the fact that numbers are a
basic category of that framework (irrespective of whether they are
logically derived from a still more basic category). As to whether
certain special types of numbers exist (in the deflated sense), that
depends on the expressive power of the framework at hand and on
whether the relevant facts can be proven. Analogous considerations
apply to the existence of physical things (the external world) given
the logico-linguistic frameworks of everyday discourse and empirical
science. (The near-tautologous nature of these categorical claims in
Carnap's hands echoes his earlier diagnosis of metaphysical
claims as pseudo-statements; see also 1934/37, Part V.A.) Unlike such
internal questions, however, external questions, questions whether
numbers or electrons "really exist" irrespective of any
framework, are ruled out as illegitimate and meaningless. The only way
in which sense could be given to them was to read them as pragmatic
questions concerned with the utility of talk about numbers or
electrons, of adopting certain frameworks. Carnap clearly retained his
basic position: existence claims remain the
province of science and there must be seen as mediated by the
available conceptual tools of inquiry. Logicians of science are in no
position to double-guess the scientists in their own proper
domain. (Needless to say, Quine 1951b opposed the internal/external distinction as much as his 1951a opposed the analytic/synthetic distinction.)



Matters came to a head with the discovery of a proof (see Craig 1956)
that the theoretical terms of a scientific theory are dispensable in
the sense of it being possible to devise a functionally equivalent
theory that does not make use of them. Did this not rob theoretical
terms of their distinctive role and so support instrumentalism? The
negative answer was twofold. As regards defending their utility,
Carnap (1963b, SS24) agreed with Hempel (1958) that in practice
theoretical terms were indispensable in facilitating inductive
relations between observational data. As regards the defense of their
cognitive legitimacy, Carnap held that this demanded determining what
he called their "experiential import", namely, determining
what specifically their empirical significance consisted in. It was
for this purpose that Carnap came to employ Ramsey's method of
regimenting theoretical terms. Nowadays this so-called ramseyfication
is often discussed as a means for expressing a position of
"structural realism", a position midway between
fully-blown scientific realism and anti-realism and so sometimes
thought to be of interest to Carnap. Carnap's own concern with
ramseyfication throws into relief not only the question of the
viability of one of the Vienna Circle's most forward-looking
stances in the debate about theoretical terms--intending to avoid
both realism and anti-realism--but also several other issues that
bear on the question of which, if any, forms of Vienna Circle
philosophy remain viable.


### 3.5 Carnap's Later Meaning Criterion and the Problem of Ramseyfication



Note that the issue of realism vis-a-vis theoretical terms is
closely related to two other issues central to the development of
Vienna Circle philosophy: Carnap's further attempts to develop a
criterion of empiricist significance for the terms of the theoretical
languages of science and his attempts to defend the distinction
between synthetic and analytic statements with regard to such
theoretical languages.



In 1956 Carnap introduced a new criterion of significance specifically
for theoretical terms (1956b). This criterion was explicitly
theory-relative. Roughly, Carnap first defined the concept of the
"relative significance" of a theoretical term. A term is
relatively significant if and only if there exists a statement in the
theoretical language that contains it as the only non-logical term and
from which, in conjunction with another theoretical statement and the
sets of theoretical postulates and correspondence rules, an
observational statement is derivable that is not derivable from that
other theoretical statement and the sets of theoretical postulates and
correspondence rules alone. Then Carnap defined the
"significance" of a theoretical term in terms of it
belonging to a sequence of such terms such that each is relatively
significant to the class of those terms that precede it in the
sequence. Now those theoretical statements were legitimate and
cognitively significant that were well-formed and whose descriptive
constants were significant the sense just specified. It is clear that
by the stepwise introduction of theoretical terms as specified, Carnap
sought to avoid the deleterious situations that rendered Ayer's
criterion false (and his own of 1928). Nevertheless, this proposal too
was subjected to criticism (e.g., Rozeboom 1960, Kaplan 1975a). A
common impression amongst philosophers appears to be that this
criterion failed as well, but this judgement is by no means
universally shared (for the majority view see Glymour 1980, for a
contrary assessment see Sarkar 2001). Thus it has been argued that
subject to some further refinements, Carnap's proposal can be
made to work (see for discussion Creath 1976, Justus 2014, Lutz 2017)--as long as the sharp
distinction between observational and theoretical terms can be
sustained. (In light of the objections to the latter distinction one
wants to add: or by a dichotomy of terms functionally equivalent to
it.)



Carnap's own position on his 1956 criterion appears somewhat
ambiguous. While he is reported to have accepted one set of criticisms
(Kaplan 1975b), he also asserted even after they had been put to him
that he thought his 1956 criterion remained adequate (1963b,
SS24b). Yet Carnap there also advised investigation of
whether still another, then entirely new approach to theoretical terms
that he was developing would allow for an improved criterion of significance
for them. So when Carnap offered "the Ramsey method" as a
method of characterizing the "empirical meaning of theoretical
terms" it was not their empirical significance as such but the
specific empirical import of theoretical terms that he considered
(1966, Ch. 26). What prompted him to undertake his investigations of
ramseyfications was not dissatisfaction with his 1956 proposal as a
criterion of significance for theoretical terms, but the fact that it still proved
impossible with this model to draw the distinction between synthetic and analytic
statements in the theoretical language. The reason for this was that
the postulates for the theoretical language also specify factual
relations between phenomena that fall under the concepts that are
implicitly defined by them. (As noted, a similar problem already had
plagued Carnap's analyses of disposition terms ever since he
allowed for non-eliminative reduction chains.)



Carnap's attempt to address this problem by ramseyfication was
published in several places from 1958 onwards. (See Carnap 1958, 1963,
SS24C-D and the popular exposition 1966, Chs. 26 and 28; compare
Ramsey 1929 and see Psillos 1999, Ch.3. This proposal and a variant of
it (1961b) were both presented in his 1959 Santa Barbara lecture
(published in Psillos 2000a); as it happened, Kaplan presented his
criticism (1975a) of Carnap's 1956 criterion at the same
conference.) With ramseyfication Carnap adverted again to entire
theories as the unit of assessment. Ramseyfication consists in the
replacement of the theoretical terms of a finitely axiomatized theory
by bound higher-order variables. This involves combining all the
theoretical postulates which define theoretical terms (call this
conjunction *T*) and correspondence rules of a theory which
link some of these theoretical terms with observational ones (call
this *C*) in one long sentence (call this *TC*) and then
replacing all the theoretical predicates that occur in it by bound
higher-order variables (call this *RTC*). This is
the so-called Ramsey-sentence of the entire theory; in it no
theoretical terms appear, but it possesses the same explanatory and
predictive power as the original theory: it has the same observational
consequences. However, Carnap stressed that the Ramsey sentence cannot
be said to be expressed in a "simple" but only an
"extended" observational language, for due to its
higher-order quantificational apparatus it includes "an advanced
complicated logic embracing virtually the whole of mathematics"
(1966, [1996, 253]).



To distinguish between analytic and synthetic statements in the
theoretical language Carnap made the following proposal. Let the
Ramsey sentence of the conjunction of all theoretical postulates and
the conjunction of all correspondence rules of that theory be
considered as expressing the entire factual, synthetic content of the
scientific theory and its terms in their entirety. By contrast, the
statement "*RTC* - *TC*"
expressed the purely analytic component of the theory, its
"A-postulate" (or so-called Carnap sentence). This
"A-postulate states that if entities exist (referred to by the
existential quantifiers of the Ramsey sentence) that are of a kind
bound together by all the relations expressed in the theoretical
postulates of the theory and that are related to observational
entities by all the relations specified by the correspondence
postulates of the theory, then the theory itself is true." Or
differently put, the A-postulate "says only that if the world is
this way, then the theoretical terms must be understood as satisfying
the theory" (1966 [1996, 271]). With *RTC*
- *TC* expressing a meaning postulate Carnap
claimed to have separated the analytic and synthetic components of a
scientific theory.



Carnap's adoption of the Ramsey method met mainly with criticism
(Psillos 1999, ch.3, 2000b, Demopoulos 2003, 2017), even though
ramseyfications continue to be discussed as a method of characterizing
theoretical terms in a realist vein (albeit with conditions not yet
introduced by Carnap, as in Lewis 1970, Papineau 1996). With
Carnap's ramseyfications, however, we do not get the answer that what exists is the structure that the ramseyfication at hand
identifies. Given the absence of a clause requiring unique
realizability, ramseyfications counseled modesty: the structure that
is identified remains indeterminate to just that degree to which
theoretical terms remain incompletely interpreted (Carnap 1961b). To
this we must add that for Carnap ramseyfications of theoretical terms
can support only internal existence claims: he explicitly reaffirmed
his confidence in the distinction between internal and external
question to defuse the realism/anti-realism issue (1966 [1996, 256]).
This strongly suggests that with these proposals Carnap did not intend
to deviate from his deflationist approach to ontology.



What must be considered, however, is that Carnap's proposal to
reconstruct the contribution of theoretical terms by ramseyfication
falls foul of arguments deriving from M.H.A. Newman's objection
to Russell's structuralism in *Analysis of Matter* (see
Demopoulos and Friedman 1985). This objection says that once they are
empirically adequate, ramseyfied theories are trivially true, given
the nature of their reconstruction of original theories. Russell held
that "nothing but the structure of the external world is
known". But if nothing is known about the generating relation
that produces the structure, then the claim that there exists such a
structure is vacuous, Newman claimed. "Any collection of things
can be organised so as to have the structure *W*, provided
there are the right number of them." (Newman 1928, 144) To see
how this so-called cardinality constraint applies to ramseyfications
of theories, note that in Carnap's hands, the non-observational
part of reconstructed theories, their theoretical entities, were
represented by "purely logico-mathematical entities, e.g.
natural numbers, classes of such, classes of classes, etc." For
him the Ramsey sentence asserted that "observable events in the
world are such that there are numbers, classes of such, etc., which
are correlated with events in a prescribed way and which have among
themselves certain relations", this being "clearly a
factual statement about the world" (Carnap 1963b, 963). Carnap
here had mathematical physics in mind where space-time points are
represented by quadruples of real numbers and physical properties like
electrical charge-density or mass-density are represented as functions
of such quadruples of real numbers.



The problem that arises from this for Carnap is not the
failure to single out the intended interpretation of the theory: as
noted, Carnap clearly thought it an advantage of the method that it
remained suitably indeterminate. The problem for Carnap is rather
that, subject to its empirical adequacy, the truth conditions of the
Ramsey-sentences are fulfilled trivially on logico-mathematical
grounds alone. As he stated, Ramsey-sentences demand that there be a
structure of entities that is correlated with observable events in the
way described. Yet given the amount of mathematics that went into the
ramseyfied theory--"virtually the whole of
mathematics"--some such structure as demanded by the
Ramsey-sentence is bound to be found among those entities presupposed
by its representational apparatus. (Here the cardinality constraint is no
constraint at all.) That any theory is trivially true for purely
formal reasons (as long as it is empirically adequate) therefore is held against
Carnap's proposal to use Ramsey sentences as reconstructions of
the synthetic content of the theoretical part of empirical scientific
theories. Given that with ramseyfications "the truth of physical
theory reduces to the truth of its observational consequences"
(Demopoulos and Friedman 1985, 635), this is a problem for
Carnap's project on its own terms: any surplus empirical meaning
of theoretical terms that Carnap sought to capture simply evaporates
(Demopoulos 2003).



This result casts its shadow over Carnap's last treatment of
theoretical terms in its entirety and threatens further consequences.
If the reconstruction of empirical theories by ramseyfication in
Carnap's fashion is unacceptable, then all explications that
build on this are called into question: explications of theoretical
analyticity as much as explications of the experiential import of
theories. If no justice has been done to the experiential
import of theoretical terms, then one must ask whether
the analytic components of a theoretical language have been correctly
identified. If they have not, then the meta-theoretical utility of the
synthetic/analytic distinction is once again be called into
question.



One is lead to wonder whether Carnap would not be well advised to
return to his 1956 position. This allowed for a criterion of empirical
significance for theoretical terms but not for the analytic/synthetic
distinction to be sustained with regard to the theoretical language.
According to Carnap's fall-back position before he hit upon
ramseyfication, it was thought possible to distinguish narrow logical
truth from factual truth in the theoretical language (1966, Ch. 28).
Yet it is difficult to silence the suspicion that an
analytic/synthetic distinction that applies only to observational
languages--and admits inescapable semantical holism for
theoretical languages--is not what the debate between Carnap and
Quine was all about. Attempts have thus been undertaken
to provide interpretations of Carnap's
ramseyfications that contain or mitigate the effects of the Newman
objection (Friedman 2008, 2011, Uebel 2011b, Creath 2012). What has become clear, in any case,
is that much is at stake for Carnap's formal explicationism,
indeed for the standard logical empiricist model of scientific
theories (see below).


### 3.6 The Status of the Criterion of Significance and the Point of the Project of Explication



We are now in a position to return to a final criticism of the search
for a criterion of empiricist significance. Much has been made of the
very status of the criterion itself (however it may be put in the
end): was it empirically testable? It is common to claim that it is
not and therefore to consign it to insignificance in turn, following
Putnam (1981a, 1981b). The question arises whether this is to overlook the fact 
that the criterion of significance was put forward not as an empirical
claim but as a meta-theoretical proposal for how to delimit empiricist
languages from non-empiricist ones. Again, pursuing this line of
inquiry is not to deny that the meaning
criterion may have been understood by some members of the Circle in such a way that it became liable
to charges of self-refutation. Even if that were the case, the reason
for this may be found not in the very idea of such a criterion, but
in the contradictory status of the Tractarian "elucidations" to which
the criterion was likened. (The legitimacy of these elucidations was
at issue already in the debates that divided the Circle in the early
1930s; see, e.g., Neurath 1932a.) What will be considered here is primarily the view of Carnap, who from 1932 onwards put his
philosophical theses in the form of "proposals" for
alternative language forms, but how the pragmatist alternative fares
will also be considered. Finally, we will consider where this does
leave neopositivist anti-metaphysics.



For Carnap, the empiricist criterion of significance was an analytic
principle, but in a very special sense. As a convention, the criterion
had the standing of an analytic statement, but it was not a formally
specifiable framework principle of the language *Ln*
to which it pertained. Properly formulated, it was a semantic
principle concerning *Ln* that was statable only in
its meta-language *L**n*+1. To argue that the
criterion itself is meaningless because it has no standing in
*Ln* is to commit a category mistake, for
meta-linguistic assertions need not have counterparts in their object
languages (Goldfarb 1997, Creath 2004, Richardson 2004). Nor would it
be correct to claim that the criterion hides circular reasoning,
allegedly because its rejection of the meaningless depends on an
unquestioned notion of experiential fact as self-explanatory (when
such fact is still to be constituted). Importantly, Carnap's
language constructor does not start with fixed notions of what is
empirical (rather than formal) or what is given (rather than assumed
or inferred), but from the beginning allows a plurality of
perspectives on these distinctions (Ricketts 1994). Carnap's
empiricist criterion of significance is precisely this: an
explication, a proposal for how empiricists may wish to speak. It is
not an explanation of how meaning arises from what is not meaningful
in itself. Unlike theorists who wish to explain how meaning itself is
constituted, explicationists can remain untroubled by the regress of
formal semantics with Tarskian strictures. For them, the lack of
formal closure (the incompleteness of arithmetic and the
inapplicability of the truth predicate to its own language) only
betokens the fact that our very own home languages cannot ever be
fully explicated.



It may be wondered whether such considerations have not become
pointless, given the troubles that attempts to provide a criterion of
significance ran into. However, as we saw, Carnap's 1956
criterion for constructed languages remains in play. Moreover, there
also remains the informal, pragmatic approach that can be applied even
more widely. Thus it is not without importance to see that pragmatic
principles delineating empirical significance (like Mach's or
Quine's Peircean insight) are not ruled out from the start
either. The reason for this is different however. For pragmatists, the
anti-metaphysical demarcation criterion is not strictly speaking a
meaning criterion. The pragmatic criterion of significance is
expressly epistemic, not semantic: it speaks of relevance with regard
to an established cognitive practice, not in-principle
truth-evaluability. This criterion is most easily expressed as a
conditional norm, alongside other methodological maxims. (If you want
your reasoning to be responsible to evidence, then avoid statements
that experience can neither confirm or disconfirm, however
indirectly.) So the suggestion that the criterion of empirical
significance can be regarded as a proposal for how to treat the
language of science cannot be brushed aside but for the persistent
neglect of the philosophical projects of Carnap or the non-formalist
left Vienna Circle.



Still, some readers may wonder whether in the course of responding to
the various counter-criticisms, the Vienna Circle's position has
not shifted considerably. This indeed is true: the attempt to show
metaphysics strictly meaningless once and for all did not succeed. For
even if Carnap's 1956 criterion and the pragmatic approach work,
they do not achieve that: Carnap's criterion only works for
constructed languages and the pragmatic one does not address the
semantic issue and only works case by case. But it can be argued that
while this debilitates the Vienna Circle's most notorious claim
(if understood without qualifications), it does not debilitate their
entire program. That was, we recall, to defend Enlightenment reason
and to counter the abuse of possibly empty but certainly
ill-understood deep-sounding language in science and in public life.
Their program was, to put it somewhat anachronistically, to promote
epistemic empowerment. This program would have been helped by an
across-the-board criterion to show metaphysics meaningless, but it can
also proceed in its absence.



But now the suspicion may be that if all that is meant to be excluded
is speculative reason without due regard to empirical and
logico-linguistic evidence, the program's success appears too
easy. Few contemporary philosophers would confess to such reckless
practices. Still, even the rejection of speculative reason is by no
means uncontroversial, as shown by the unresolved status of the appeal
to intuitions that characterizes much of contemporary analytical
metaphysics and epistemology. Moreover, much depends on what's
considered to be "due regard": is merely bad science
"metaphysics"? Or only appeals to the supernatural? And
what about *de re* necessities? Or the seeming commitments of
existential quantification? The promotion of anti-metaphysics may be
applauded in principle as an exercise in intellectual hygiene, the
objection goes, but in practice it excludes either too much or too
little: it either cripples our understanding of theoretical science or
normalizes away the Vienna Circle's most notorious claim.



In response it is helpful to consider the conception of metaphysics
that can be seen to be motivating much of the Circle's ethical
non-cognitivism. What did Carnap (1935) and Neurath (1932a) dismiss
when they dismissed normative ethics as metaphysical and cognitively
meaningless? One may concede that due to the brusque way in which they
put their broadly Humean point, they opened themselves up to
significant criticism, but it is very important to see also what they
did not do. Most notably, they did not dismiss as meaningless all
concern with how to live. Conditional prescriptions remained
straight-forwardly truth-evaluable in instrumental terms and so
cognitively meaningful. In addition, their own active engagement for
Enlightenment values in public life showed that they took these
matters very seriously themselves. (In fact, their engagement as
public intellectuals compares strikingly with that of most
contemporary philosophers of science.) But neither did they fall
victim to the naturalistic fallacy nor were they simply inconsistent.
In the determination of basic values they rather saw acts of personal
self-definition, but, characteristically, Carnap showed a more
individualistic and Neurath a more collectively oriented approach to the
matter. What needs to be borne in mind, then, is the meaning that they
attached to the epithet "metaphysical" in this and other
areas: the arrogation of unique and fully determined objective insight
into matters beyond scientific reason. It was in the ambition of
providing such unconditional prescriptions that they saw philosophical
ethics being the heir of theology. (Compare Carnap 1935 and 1963b,
SS32 and Neurath 1932a and 1944, SS19.) Needless to say, it
remains contentious to claim those types of philosophical ethics to be
cognitively meaningless that seek to derive determinate sets of codes
from some indisputable principle or other. But the ongoing discussion
of non-cognitivism and its persistent defense in analytical ethics as "expressivism"
suggest that, understood as outlined, the Circle's
non-cognitivism was by no means absurd or contradictory.



It may be noted here that a newly discovered fragment of
Carnap's writing (2017) has given fresh impetus to explorations
of the model of ethical reasoning in terms of optatives that Carnap
outlined (1963b, SS32) in response to A. Kaplan's criticism
(1963) of his earlier position. What emerges is that Carnap was
prepared to integrate ethical desiderata among non-ethical ones within
the network of means and ends that decision theory as a normative
theory of rational action seeks to systematize and regiment. Moral
reasoning is assimilated to practical reasoning and no longer suffers
from a deficit of significance--albeit at the cost of not being
able to exclude appeals to certain types of intrinsic value on the ground their being beyond the pale (see Carus 2017). Carnap
may reasonably respond here that as a theorist of science he is not
required to account for normative ethics beyond providing a framework
for understanding its undeniable role in a generic theory of human
behavior. What was rightly objected against his earlier position was
that it made such understanding impossible.



Whatever the details, their non-cognitivism supports the idea that the
left wing's anti-metaphysics was primarily deflationist. They opposed all claims to have a categorically deeper
insight into reality than either empirical or formal science, such
that philosophy would stand in judgement of these sciences as to their
reality content or that mere science would stand in need of
philosophical interpretations. (Concerned with practical problems,
they likewise opposed philosophical claims to stand above the
contestations of mere mortals.) Importantly, such deflationism need
not remain general and vague, but can be given precise content. For
instance, it has been argued (Carus 1999) that Carnap was correct to understand Tarski's theory of truth not as a traditional
correspondence theory such that truth consisted in some kind of
agreement of statements or judgements and facts or the world where the
latter make true the former. In Carnap's unchanged opposition to
the classical correspondence theory of truth in turn lies not only the
continuity between his own syntactic and semantic phases, but also the
key to his and the entire left Vienna Circle's understanding of
their anti-metaphysical campaign. (On various occasions in the early
30s, Hahn, Frank and Neurath opposed correspondence truth very
explicitly, while, in later years, Neurath resisted Tarskian semantics
precisely because he wrongly suspected it of resurrecting
correspondentism and Frank continued to castigate correspondentism
whenever required. On this tangled issue, see Mormann 1999, Uebel
2004, Mancosu 2008.)



This suggests that a hard core of Viennese anti-metaphysics survives
the criticism and subsequent qualifications of early claims made for
their criteria of empirical significance, yet retains sufficient
philosophical teeth to remain of contemporary interest. The
metaphysics which the left wing attacked, besides everyday
supernaturalism and the supra-scientific essentialism of old, was the
correspondence conception of truth and associated realist conceptions
of knowledge. These notions were deemed attackable directly on
epistemological grounds, without any diversion through the theory of
meaning: how could such correspondences or likenesses ever be
established? As Neurath liked to put it (1930), we cannot step outside
of our thinking to see whether a correspondence obtains between what
we think and how the world is. (Against defenses of the correspondence
theory by arguments from analogy it would be argued that the
analogy is overextended.) Against the counter that this is merely an
epistemic argument that does not touch the ontological issue Neurath
is likely to have argued that doing without an epistemic account is a
recipe for uncontrollable metaphysics.



Importantly, the left wing's deflationary anti-metaphysics was
accompanied by a distinctively constructivist attitude. Here one must
hasten to add, of course, that what was constructed were not the
objects of first-order discourse (tables, chairs, electrons and black
holes) but concepts, be they concepts associated with technical terms for observables, theoretical terms or terms needed for reflection
about the cognitive enterprise of science (ideas like evidence and its
degrees and presuppositions). As meta-theorists of science they
developed explications: different types of explications were
envisaged, ranging from analytic definitions giving necessary and
sufficient conditions in formal languages all the way to pragmatic,
exemplar-based criterial delimitations of the central applications of
contested concepts or practices. Two branches of the Circle's
constructivist tendency can thus be distinguished: Carnap's
rational reconstructions and formalist explications and
Neurath's and Frank's empirically informed and
practice-oriented reconceptualizations. The difference between these
two approaches can be understood as a division
of labor between the tasks of exploring logico-linguistic
possibilities of conceptual reconstruction and considering the
efficacy of particular scientific practices. In principle, the
constructivist tendency in Vienna Circle philosophy was able to
embrace both (compare Carnap 1934/37, SS72 and Neurath 1936b).
However, in its own day, this two-track approach remained
incompletely realized as philosophical relations between Carnap and
Neurath soured over disputes stemming from mutual misunderstandings.
Frank's final paper (1963) was a terse reminder that the logic
of science was not the sole successor or replacement of traditional
philosophy and Carnap's response (1963b, SS3) again acknowledged the compatibility in principle of his logic of science and what Frank called the "pragmatics of science" (1957). 



Considering the Vienna Circle as a whole in the light of this reading
of its anti-metaphysical philosophy, we find the most striking
division within it yet. Unlike Carnap and the left wing, Schlick had
little problem with a correspondence theory of truth once it was
cleansed of psychologistic and intuitive accretions and centered on
the idea of unique coordination of statement and fact. In this lay the
strongest sense of continuity between his pre-Vienna Circle
*General Theory of Knowledge* (1918/25) and his post-Tractarian
epistemology (1935a, 1935b). (Schlick also showed little enthusiasm
for the constructivist tendencies which already the manifesto of 1929
had celebrated.) Allowing for some simplification, it must be noted
that Schlick's attack on metaphysics (which gradually weakened
anyway) presupposed a non-constructivist reading of the criterion of
significance. Whether his conception can escape the charge
self-refutation must be left open here.


### 3.7 The Vienna Circle and History



Much confusion exists concerning the Vienna Circle and history, that
is, both concerning the Vienna Circle's attitude towards the
history of philosophy and science and concerning its own place in that
history. As more has been learnt about the history of the Vienna
Circle itself--the development and variety of its doctrines as
well as its own prehistory as a philosophical forum--this
confusion can be addressed more adequately.



As the unnamed villain of the opening sentences of Kuhn's
influential *Structure of Scientific Revolutions* (1962),
logical empiricism is often accused of lacking historical
consciousness and any sense of the embedding of philosophy and science
in the wider culture of the day. Again it can hardly be denied that
much logical empiricist philosophy, especially after World War II, was
ahistorical in outlook and asocial in its orientation.
Reichenbach's distinction (1938) between the contexts of
discovery and justification--which echoed distinctions made since
Kant (Hoyningen-Huene 1987) and was already observed under a different
name by Carnap in the *Aufbau*--was often employed to
shield philosophy not only from contact with the sciences as practiced
but also culture at large. But this was not the case for the Vienna
Circle generally. On the one hand, unlike Reichenbach, who drew a
sharp break between traditional philosophy and the new philosophy of
logical empiricism in his popular *The Rise of Scientific
Philosophy* (1951), Schlick was very much concerned to stress the
remaining continuities with traditional philosophy and its cultural
mission in his last paper (1938). On the other hand, on the left wing
of the Circle scientific meta-theory was opened to the empirical
sciences. To be sure, Carnap for his own part was happy to withdraw to
the "icy slopes" of the logic of science and showed no
research interest of his own in the history of science or philosophy,
let alone its social history. By way of the division of labor he left
it to Neurath and Frank to pursue the historical and practice-related
sociological questions that the pure logic of science had to leave
unaddressed. (See, e.g., Neurath's studies of the history of
optics (1915, 1916), Frank's homage to Mach (1917), his
pedagogical papers in (1949b) and his concern with the practice of
theory acceptance and change in (1956); cf. Uebel 2000 and Nemeth
2007.) Moreover, it must be noted that Neurath himself all along had
planned a volume on the history of science for the International
Encyclopedia of Science, a volume that in the end became Kuhn's
*Structure*. Its publication in this series is often regarded as supremely ironical, given
how Kuhn's book is commonly read. But this is not only to
overlook that the surviving editors of that series, Carnap and Morris
were happy to accept the manuscript, but also that Carnap found himself in
positive agreement with Kuhn (Reisch 1991, Irzik and
Grunberg 1995; cf. Friedman 2001). Finally, one look at the 1929
manifesto shows that its authors were very aware of and promoted the
links between their philosophy of science and the socio-political and
cultural issues of the day.



Turning to the historical influences on the Vienna Circle itself, the
scholarship of recent decades has unearthed a much greater variety
than was previously recognized. Scientifically, the strongest
influences belonged to the physicists Helmholtz, Mach and Boltzmann,
the mathematicians Hilbert and Klein and the logicians Frege and
Russell; amongst contemporaries, Einstein was revered above all
others. The Circle's philosophical influences extend far beyond
that of the British empiricists (especially Hume), to include the
French conventionalists Henri Poincare, Pierre Duhem and Abel
Rey, American pragmatists like James and, in German-language
philosophy, the Neo-Kantianism of both the Heidelberg and the Marburg
variety, even the early phenomenology of Husserl as well as the
Austrian tradition of Bolzano's logic and the Brentano school.
(See Frank 1949a for the influence of the French conventionalists; for the importance of
Neo-Kantianism for Carnap, see Friedman 1987, 1992, Sauer 1989,
Richardson 1998, Mormann 2007; for Neo-Kantianism in Schlick, see
Coffa 1991, Ch. 9 and Gower 2000; for the significance of Husserl for
Carnap, see Sarkar 2004, Ryckman 2007, Carus 2016, Dambock 2018; for the influence of and sympathies for pragmatism see Frank 1949a and Uebel 2016; the Bolzano-Brentano
connection is explored in Haller 1986.) It is against this very wide
background of influences that the seminal force must be assessed that
their contemporary Wittgenstein exerted. The literature on the
relation between Wittgenstein and the Vienna Circle is vast but very
often suffers from an over-simplified conception of the latter. (See
Stern 2007 for an attempt by a Wittgenstein scholar to redress the
balance.) Needless to say, different wings of the Circle show these
influences to different degrees. German Neo-Kantianism was important
for Schlick and particularly so for Carnap, whereas the Austrian
naturalist-pragmatist influences were particularly strong on Hahn,
Frank and Neurath. Frege was of great importance for Carnap, less so
for Hahn who looked to Russell. Most importantly, by no means all
members of the Vienna Circle sought to emulate Wittgenstein--thus
the division between the faction around Schlick and the left wing (see Uebel 2017).



While these findings leave numerous questions open, they nevertheless refute the standard picture of Vienna Circle philosophy which confuses A.J. Ayer's
*Language, Truth and Logic* with the real thing. Ayer offered a version of British empiricism (Berkeley's epistemic phenomenalism updated with Russellian logic) and paid no attention, for instance, to the Circle's overarching concern with establishing
the objectivity claim of science. Ayer's remark in the
preface to his later anthology *Logical Positivism* that his own *Language, Truth and Logic* "did
something to popularize what may be called the classical position of
the Vienna Circle" (1959b, 8) is highly misleading therefore. What he
called "the classical position" was at best a partial characterisation of the starting
position of some--by no means all--of its members, a position which by 1932 the left
wing as a whole rejected and even Schlick had no reason to
endorse any longer.



All that said by way of embedding the Vienna Circle's philosophy
in its time, one must also ask whether its members understood their
own position correctly. Here one issue in particular has become
increasingly prominent and raises questions that are of importance for
philosophy of science still today. That is whether, after all, logical
empiricism did have the resources to understand correctly the then
paradigm modern science, the general theory of relativity. According
to the standard logical empiricist story (Schlick 1915, 1917, 1921,
1922), their theory conclusively refuted the Kantian conception of the
synthetic *a priori*: Euclidean geometry was not only one
geometry amongst many, it also was not the one that characterized
empirical reality. With one of its most prominent exemplars refuted,
the synthetic *a priori* was deemed overthrown altogether. As
noted, Schlick convinced the young Reichenbach to drop his residually
Kantian talk of constitutive principles and speak of conventions
instead. Likewise Schlick rejected efforts by Ernst Cassirer (see his
1921, developing themes from his 1910) to make do with a merely
relative *a priori* in helping along scientific
self-reflection. Even though much later, and on the independent
grounds of quantum physics, Frank attested to the increased proximity
of his and Cassirer's understanding of scientific theories
(1938), Schlick's disregard of Cassirer's efforts remains
notable.



Most controversial is how the issue of general relativity as a
touchstone for competing philosophies of science was framed: having
dismissed Kant's own synthetic *a priori* for its
mistaken apodicity, no time was spared for discussion of its then
contemporary development in Neo-Kantianism as a merely relative but
still constitutive *a priori*. Now in the philosophy of
physics, this omission--committed both by Schlick and
Reichenbach--has recently come back to haunt logical empiricists
with considerable vengeance. Thus it has been argued that the
Schlick-Reichenbach reading of general relativity as embodying the
standard logical empiricist model of scientific theories, with high
theory linked to its observational strata by purely conventional
coordinative definitions, is deeply mistaken in representing the local
metric of space-time not to be empirically but conventionally
determined as in special relativity (Ryckman 1992) and that
it is instead only the tradition of transcendental idealism that
possesses the resources to understand the achievements of mathematical
physics (Ryckman 2005; cf. Friedman 2001). It is tempting to speak of
the return of the repressed Neo-Kantian opposition. But it is tempting
too to note that Schlick's and Reichenbach's mistake was
already corrected quietly and without fanfare by Carnap (see the
example in his 1934/37, SS50). Clearly then, the mistake was not
inevitable and inherent in logical empiricist theorizing about
science as such. (For discussion of different criticism of the Circle's reading of Einstein, especially his relation to Mach, see DiSalle 2006, Ch.4.)



The charge of a constitutive failing would rather seem to come from
Demopoulos's challenge to the two-languages model (nearly)
universally adopted in logical empiricism (forthcoming). Importantly,
this challenge does not proceed, as some previous ones have, from the
impossibility of drawing a sharp distinction between the observational and the theoretical (Putnam
1962). Rather, the two-languages model falsely supposes that the
process of testing scientific hypotheses must only advert to
theoretically uncontaminated facts and so results in misunderstanding
the empirical import of theoretical claims (as in the Newman problem).
Instead, a conception of theory-mediated measurement and testing is
suggested that extends responsiveness to observational data to
theoretical claims by showing them to be essentially implicated in the
production of observed experimental consequences. Hoping to advance
beyond the stalemate between realism and instrumentalism without
appealing to question-begging semantics, Demopoulos here breaks with a
supposition upheld by Carnap throughout, namely that the theoretical
language be regarded as an essentially uninterpreted, at best partially
interpreted calculus. Whatever the outcome of this challenge, it is
remarkable how on this far-reaching and fundamental issue contemporary
philosophy of science intersects with the history of philosophy of
science.


## 4. Concluding Remarks



In conclusion, the results of the discussions in section 3 can be
briefly summarised. To start with, the dominant popular picture of the
Vienna Circle as a monolithic group of simple-minded verificationists
who pursued a blandly reductivist philosophy with foundationalist
ambitions is widely off the mark. Instead, the Vienna Circle must be
seen as a forum in which widely divergent ideas about how empiricism
can cope with modern empirical and formal science were discussed.
While by no means all of the philosophical initiatives started by
members of the Vienna Circle have born fruit, it is neither the case
that all of them have remained fruitless. Nor is it the case that
everything once distinctive of Vienna Circle philosophy has to be
discarded.



Consider verificationism. While the idea to show metaphysics
once-and-for-all and across-the-board to be not false but
meaningless--arguably the most distinctive thesis associated with
the Vienna Circle--did indeed have to be abandoned, two elements
of that program remain so far unrefuted. On the one hand, it remains
an option to pursue the search for a criterion of empirical
significance in terms of constructed, formal languages further along
the lines opened by Carnap with his theory-relative proposal of 1956
(and its later defense against critics). On the other
hand--albeit at the cost of merging with the pragmatist tradition
and losing the apparent Viennese distinctiveness--the option to
neglect as cognitively irrelevant, and in this sense metaphysical, all
assertions whose truth or falsity would not make a difference remains
as open as it always was. In addition it must be noted that, properly
formulated, neither the formalist version of the criterion of
empirical significance for constructed languages nor the pragmatist
version of the criterion for natural languages are threatened by
self-refutation.



Consider analyticity. Here again, the traditional idea--sometimes
defended by some members--did show itself indefensible, but this
leaves Carnap's framework-relative interpretation of analyticity
and the understanding of the *a priori* as equally relative
to be explored. As noted, if Carnap's ramseyfications can be
defended, an analytic/synthetic distinction could be upheld also for
the theoretical languages of science. In any case, however, the
distinction between framework principles and content continues to be
drawable on a case by case basis.



Consider reductionism and foundationalism. While it cannot be denied
that various reductionist projects were at one time or another
undertaken by members of the Vienna Circle and that not all of its
members were epistemological anti-foundationalists either from the
start or at the end, it is clearly false to paint all of them with
reductivist and/or foundationalist brushes. This is particularly true
of the members of the so-called left wing of the Circle, all of whom
ended up with anti-foundationalist and anti-reductionist positions
(even though this did involve instrumentalism for some).



Consider also, however, the challenges mentioned above to the
fundamental tenets of logical empiricism that remain issues of intense
discussion: challenges to its conception of the nature of empirical
theory and of what is distinctive about the formal sciences. That to
this day no agreement has been reached about how its proposals are to
be replaced is not something that is unique to logical empiricism as a
philosophical movement, but that they remain on the table, as it were,
shows the ongoing relevance and centrality of its work for philosophy
of science.



Whether the indicated qualifications and/or modifications count as
defeats of the original project depends at least in part on what
precisely is meant to be rejected when metaphysics is rejected and
that in turn depends on what the positive vision for philosophy
consists in. Here again one must differentiate. While some members
ended with considerable more sympathy for traditional philosophy than
they displayed in the Circle's heyday--and may thus be
charged with partial surrender--others stuck to their guns. For
them, what remained of philosophy stayed squarely in the deflationist
vein established by the linguistic turn. They offered explications of
contested concepts or practices that, they hoped, would prove useful.
Importantly, the explications given can be of two sorts: the formal
explications of the logic of science by means of exemplary models of
constructed languages, and the more informal explications of the
empirical theory of science given by spelling out how certain
theoretical desiderata can be attained more or less under practical
constraints. This has been designated as the bipartite metatheory
conception of scientific philosophy and ascribed to the left wing of
the Circle as an ideal unifying its diverse methodologies (Uebel 2007,
Ch. 12, 2015). Readers will note therefore that despite his enormous
contribution to the development of Vienna Circle philosophy, it is not
Schlick's version of it that appears to this reviewer to be of
continuing relevance to contemporary philosophy--unlike, in their
very different but not incompatible ways, Carnap's and
Neurath's and Frank's. This may be taken as a partial
endorsement of Hempel's 1991 judgement (quoted in sect. 1
above), against which, however, Carnap has here been re-claimed for
the Neurathian wing.



Needless to say, recent work on Vienna Circle philosophies continues
to inspire a variety of approaches to the legacy they constitute
(besides prompting continuing excavations of other members'
non-standard variants; e.g., on Feigl see Neuber 2011). There is
Michael Friedman's extremely wide-ranging project (2001, 2010,
2012) to use the shortcomings of Vienna Circle philosophies as a
springboard for developing a renewed Kantian philosophy that also
overcomes the failings of neo-Kantianism and provides a
philosophy-cum-history fit for our post-Kuhnian times. Then there is
Richardson's proposal (2008) to turn the ambition to develop a
scientific philosophy into a research programme for the history of
science, so as to reveal more clearly the real world dynamics and
limitations of philosophy as a scientific metatheory. And there is
Carus's suggestion (2007) that Carnap's minimalist
explicationism be placed in the service of a renewed Enlightenment
agenda (continuing the task of the "scientific world
conception"). This connects with the current metaphilosophical interest in conceptual engineering, the relevance of Carnap's work to which becoming increasingly recognised (Justus 2012, Wagner 2012, Brun 2016, Reck and Dutilh Novaes 2017, Dutilh Novaes forthcoming, Lutz forthcoming). All along, of course, Vienna Circle philosophies
also continue to serve as foils for alternative and self-consciously
post-positivist programs, fruitfully so when informed by the results of recent
scholarship (e.g. Ebbs 2017).



It would appear then that despite continued resistance to recent
revisionist scholarship--a resistance that consists not so much
in contesting but in ignoring its results--the fortune of Vienna
Circle philosophy has turned again. Restored from the numerous
distortions of its teachings that accrued over generations of acolytes
and opponents, the Vienna Circle is being recognized again as a force
of considerable philosophical sophistication. Not only is it the case
that its members profoundly influenced the actual development of
analytical philosophy of science with conceptual initiatives that,
typically, were seen through to their bitter end. It is also the case
that some of its members offered proposals and suggested approaches
that were not taken up widely at the time (if at all), but that are
relevant again today. Much like its precursors Frege, Russell and
Wittgenstein, the conventionalists Poincare and Duhem, the
pragmatists Peirce and Dewey--and like its contemporaries from
Reichenbach's Berlin Group and the Warsaw-Lvov school of logic
to the Neo-Kantian Cassirer--the Vienna Circle affords a valuable
vantage point on contemporary philosophy of empirical and formal
science.