## 1. Life



Karl Raimund Popper was born on 28 July 1902 in Vienna. His parents,
who were of Jewish origin, brought him up in an atmosphere which he
was later to describe as "decidedly bookish". His father
was a lawyer by profession, but he also took a keen interest in the
classics and in philosophy, and communicated to his son an interest in
social and political issues. His mother inculcated in him such a
passion for music that for a time he contemplated taking it up as a
career; he initially chose the history of music as a second subject
for his Ph.D. examination. Subsequently, his love for music became one
of the inspirational forces in the development of his thought, and
manifested itself in his highly original interpretation of the
relationship between dogmatic and critical thinking, in his account of
the distinction between objectivity and subjectivity, and, most
importantly, in the growth of his hostility towards all forms of
historicism, including historicist ideas about the nature of the
"progressive" in music. The young Karl attended the local
*Realgymnasium*, where he was unhappy with the standards of the
teaching, and, after an illness he left to attend the University of
Vienna in 1918, matriculating four years later. In 1919 he became
heavily involved in left-wing politics and became for a time a
Marxist. However, he was quickly disillusioned with the doctrinaire
character of the latter, and soon abandoned it entirely. He also
discovered the psychoanalytic theories of Freud and Adler (he served
briefly as a voluntary social worker with deprived children in one of
the latter's clinics in the 1920s), and heard Einstein lecture
on relativity theory. The dominance of the critical spirit in
Einstein, and its total absence in Marx, Freud and Adler, struck
Popper as being of fundamental importance: the pioneers of
psychoanalysis, he came to think, couched their theories in terms
which made them amenable only to confirmation, while Einstein's
theory, crucially, had testable implications which, if false, would
have falsified the theory itself.



Popper took some time to settle on a career; he trained as a
cabinetmaker, obtained a primary school teaching diploma in 1925 and
qualified to teach mathematics and physics in secondary school in
1929. He undertook a doctoral programme with the department of
psychology at the University of Vienna, then under the supervision of
Karl Buhler, one of the founder members of the Wurzburg
school of experimental psychology. Popper's project was
initially designed as a psychological investigation of human memory,
on which he conducted initial research. However, the subject matter of
a planned introductory chapter on methodology assumed a position of
increasing pre-eminence and this resonated with Buhler, who, as a
Kant scholar (a professor of philosophy and psychology), had famously
addressed the issue of the contemporary "crisis in
psychology". This "crisis", for Buhler, related
to the question of the unity of psychology and had been generated by
the proliferation of then competing paradigms within the discipline
which had undermined the hitherto dominant associationist one and
problematized the question of method. Accordingly, under
Buhler's direction, Popper switched his topic to the
methodological problem of cognitive psychology and received his
doctorate in 1928 for his dissertation "Zur Methodenfrage der
Denkpsychologie". In extending Buhler's Kantian
approach to the crisis in the dissertation, Popper critiqued Moritz
Schlick's neutral monist programme to make psychology scientific
by transforming it into a science of brain processes. This latter
ideal, Popper argued, was misconceived, but the issues raised by it
ultimately had the effect of refocusing Popper's attention away
from Buhler's question of the unity of psychology to that
of its scientificity. This philosophical focus on questions of method,
objectivity and claims to scientific status was to become a principal
life-long concern, bringing the orientation of Popper's thought
into line with that of such contemporary "analytic"
philosophers as Frege and Russell as well as that of many members of
the Vienna Circle.



Popper married Josephine Anna Henninger ("Hennie") in
1930, and she also served as his amanuensis until her death in 1985.
At an early stage of their marriage they decided that they would never
have children. In 1937 he took up a position teaching philosophy at
the University of Canterbury in New Zealand, where he was to remain
for the duration of the Second World War.



The annexation of Austria in 1938 became the catalyst which prompted
Popper to refocus his writings on social and political philosophy. He
published *The Open Society and Its Enemies*, his critique of
totalitarianism, in 1945. In 1946 he moved to England to teach at the
London School of Economics, and became professor of logic and
scientific method at the University of London in 1949. From this point
on his reputation and stature as a philosopher of science and social
thinker grew, and he continued to write prolifically--a number of
his works, particularly *The Logic of Scientific Discovery*
(1959), are now widely seen as pioneering classics in the field.
However, he combined a combative personality with a zeal for
self-aggrandisement that did little to endear him to professional
colleagues. He was ill-at-ease in the philosophical milieu of post-war
Britain which was, as he saw it, fixated with trivial linguistic
concerns dictated by Wittgenstein, whom he considered his nemesis.
Popper's commitment to the primacy of rational criticism was
counterpointed by hostility towards anything that amounted to less
than total acceptance of his own thought, and in Britain--as had
been the case in Vienna--he increasingly became an isolated
figure, though his ideas continued to inspire admiration.



In later years Popper came under philosophical criticism for his
prescriptive approach to science and his emphasis on the logic of
falsification. This was superseded in the eyes of many by the
socio-historical approach taken by Thomas Kuhn in *The Structure of
Scientific Revolutions* (1962). In that work, Kuhn, who argued for
the incommensurability of rival scientific paradigms, denied that
science grows linearly through the accumulation of truths.



Popper was knighted in 1965, and retired from the University of London
in 1969, remaining active as a writer, broadcaster and lecturer until
his death in 1994. (For more detail on Popper's life, see his
*Unended Quest* [1976]).


## 2. Backdrop to Popper's Thought



A number of biographical features may be identified as having a
particular influence upon Popper's thought. His teenage
flirtation with Marxism left him thoroughly familiar with the Marxian
dialectical view of economics, class-war, and history. But he was
appalled by the failure of the democratic parties to stem the rising
tide of fascism in Austria in the 1920s and 1930s, and the effective
welcome extended to it by the Marxists, who regarded fascism as a
necessary dialectical step towards the implosion of capitalism and the
ultimate victory of communism. *The Poverty of Historicism*
(1944; 1957) and *The Open Society and Its Enemies* (1945),
Popper's most impassioned and influential social works, are
powerful defences of democratic liberalism, and strident critiques of
philosophical presuppositions underpinning all forms of
totalitarianism.



Popper was also profoundly impressed by the differences between the
allegedly "scientific" theories of Freud and Adler and the
revolution effected by Einstein's theory of Relativity in
physics in the first two decades of the twentieth century. The main
difference between them, as Popper saw it, was that while
Einstein's theory was highly "risky", in the sense
that it was possible to deduce consequences from it which were, in the
light of the then dominant Newtonian physics, highly improbable (e.g.,
that light is deflected towards solid bodies--confirmed by
Eddington's experiments in 1919), and which would, if they
turned out to be false, falsify the whole theory, nothing could, even
*in principle*, falsify psychoanalytic theories. They were,
Popper argues, "simply non-testable, irrefutable. There was no
conceivable human behaviour which could contradict them" (1963:
37). As such, they have more in common with myths than with genuine
science; "They contain most interesting psychological
suggestions, but not in a testable form" (1963: 38). What is
apparently the chief source of strength of psychoanalysis, he
concluded, viz. its capability to accommodate and explain every
possible form of human behaviour, is in fact a critical weakness, for
it entails that it is not, and could not be, genuinely predictive. To
those who would respond that psychoanalytic theory is supported by
clinical observations, Popper points out that



> 
> 
> ... real support can be obtained only from observations
> undertaken as tests (by 'attempted refutations'); and for
> this purpose *criteria of refutation* have to be laid down
> beforehand: it must be agree which observable situations, if actually
> observed, mean that the theory is refuted. (1963: 38, footnote 3)
> 
> 
> 



Popper also considers that contemporary Marxism also lacks scientific
status. Unlike psychoanalysis, he argues, Marxism had been initially
scientific, in that it was genuinely predictive. However, when these
predictions were not in fact borne out, the theory was saved from
falsification by the addition of *ad hoc* hypotheses which made
it compatible with the facts. By this means, Popper asserts, a theory
which was initially genuinely scientific degenerated into
pseudo-scientific dogma. As he sees it, the Hegelian dialectic was
adopted by Marxists not to oppose dogmatism but to accommodate it to
their cause by eliminating the possibility of contradictory evidence.
It has thus become what Popper terms "reinforced
dogmatism" (1963: 334).



These factors combined to make Popper take *falsifiability* as
his criterion for demarcating science from non-science: if a theory is
incompatible with possible empirical observations it is scientific;
conversely, a theory which is compatible with all such observations,
either because, as in the case of Marxism, it has been modified solely
to accommodate such observations, or because, as in the case of
psychoanalytic theories, it is consistent with all possible
observations, is unscientific. However, Popper is not a positivist and
acknowledges that unscientific theories may be enlightening and that
even purely mythogenic explanations have performed a valuable function
in the past in expediting our understanding of the nature of
reality.


## 3. The Problem of Demarcation



For Popper the central problem in the philosophy of science is that of
demarcation, i.e., of distinguishing between science and what he terms
"non-science" (e.g., logic, metaphysics, psychoanalysis,
and Adler's individual psychology). Popper is unusual amongst
contemporary philosophers in that he *accepts* the validity of
the Humean critique of induction, and indeed, goes beyond it in
arguing that induction is never actually used in science. However, he
does not concede that this entails scepticism and argues that the
Baconian/Newtonian insistence on the primacy of "pure"
observation, as the initial step in the formation of theories, is
completely misguided: all observation is selective and theory-laden
and there are no pure or theory-free observations. In this way he
destabilises the traditional view that science can be distinguished
from non-science on the basis of its inductive methodology. In
contradistinction to this, Popper holds that there is no unique
methodology specific to science; rather, science, like virtually every
other organic activity, consists largely of problem-solving.



Popper accordingly rejects the view that induction is the
characteristic method of scientific investigation and inference,
substituting *falsifiability* in its place. It is easy, he
argues, to obtain evidence in favour of virtually any theory, and he
consequently holds that such "corroboration", as he terms
it, should count scientifically only if it is the positive result of a
genuinely "risky" prediction, which might conceivably have
been false. In a critical sense, Popper's theory of demarcation
is based upon his perception of the asymmetry which, at the level of
logic, holds between verification and falsification: it is logically
impossible to verify a universal proposition by reference to
experience (as Hume saw clearly), but a single genuine
counter-instance falsifies the corresponding universal law. In a word,
an exception, far from "proving" a rule, conclusively
refutes it.



Every genuine scientific theory then, in Popper's view, is
*prohibitive*, because the theories of natural science take the
form of universal statements. "All *A*s are
*X*" is equivalent to "No *A* is
not-*X*" which is falsified if "Some *A* is
not-*X*" turns out to be true. For example, the law of
the conservation of energy can be expressed as "There is no
perpetual motion machine".



However, the universality of such laws, he argues, does rule out the
possibility of their verification. Thus, a theory that has withstood
rigorous testing should be deemed to have received a high measure of
corroboration. and may be retained provisionally as the best available
theory until it is finally falsified and/or is superseded by a better
theory.



Popper stresses in particular that there is no unique way, no single
method such as induction, which functions as the route to scientific
theory, and approvingly cites Einstein on that point:



> 
> 
> There is no logical path leading to [the highly universal laws of
> science]. They can only be reached by intuition, based upon something
> like an intellectual love of the objects of experience. (2002:
> 8-9)
> 
> 
> 



Science, in Popper's view, starts with problems rather than with
observations--it is, indeed, precisely in the context of
grappling with a problem that the scientist makes observations in the
first instance: his observations are selectively designed to test the
extent to which a given theory functions as a satisfactory solution to
a given problem.



On this criterion of demarcation physics, chemistry, and
(non-introspective) psychology, amongst others, are classified as
sciences, psychoanalysis is a pre-science and astrology and phrenology
are pseudo-sciences.


## 4. Basic Statements, Falsifiability and Convention



Popper draws a clear distinction between the *logic* of
falsifiability and its *applied methodology*. The logic of his
theory is utterly simple: a universal statement is falsified by a
single genuine counter-instance. Methodologically, however, the
situation is complex: decisions about whether to accept an apparently
falsifying observation as an actual falsification can be problematic,
as observational bias and measurement error, for example, can yield
results which are only apparently incompatible with the theory under
scrutiny.



Thus, while advocating falsifiability as the criterion of demarcation
for science, Popper explicitly allows for the fact that in practice a
single conflicting or counter-instance is never sufficient
methodologically for falsification, and that scientific theories are
often retained even though much of the available evidence conflicts
with them, or is anomalous with respect to them.



In this connection, in the *Logic of Scientific Discovery*
Popper introduces the technical concept of a "basic
statement" or "basic proposition", which he defines
as a statement which can serve as a premise in an empirical
falsification and which takes the singular existential form
"There is an *X* at *Y*". Basic statements
are important because they can formally *contradict* universal
statements, and accordingly play the role of potential falsifiers. To
take an example, the (putative) basic statement "In space-time
region *k* there is an apparatus which is a perpetual motion
machine" contradicts the law of the conservation of energy, and
would, if true, falsify it (2002: 48). Accordingly, Popper holds that
basic statements are objective and are governed by two requirements:
(a) the formal, that they must be both *singular* and
*existential* and (b) the material, that they must be
intersubjectively testable.



In essence, basic statements are for Popper logical constructs which
embrace and include 'observation statements', but for
methodological reasons he seeks to avoid that terminology, as it
suggests that they are derived directly from, and known by, experience
(2002: 12, footnote 2), which would conflate them with the
"protocol" statements of logical positivism and
reintroduce the empiricist idea that certain kinds of experiential
reports are incorrigible. The "objectivity" requirement in
Popper's account of basic statements, by contrast, amounts to a
rejection of the view that the truth of scientific statements can ever
be reduced to individual or collective human experience. (2002:
25).



Popper therefore argues that there are no statements in science which
cannot be interrogated: basic statements, which are used to test the
universal theories of science, must themselves be inter-subjectively
testable and are therefore open to the possibility of refutation. He
acknowledges that this seems to present a practical difficulty, in
that it appears to suggest that testability must occur *ad
infinitum*, which he acknowledges is an operational absurdity:
sooner or later all testing must come to an end. Where testing ends,
he argues, is in a convention-based decision to accept a basic
statement or statements; it is at that point that convention and
intersubjective human agreement play an indispensable role in
science:



> 
> 
> Every test of a theory, whether resulting in its corroboration or
> falsification, must stop at some basic statement or other which we
> *decide to accept*. If we do not come to any decision, and do
> not accept some basic statement or other, then the test will have led
> nowhere. (2002: 86)
> 
> 
> 



However, Popper contends that while such a decision is usually
*causally related* to perceptual experience, it is not and
cannot be *justified* by such experience; basic statements are
experientially underdetermined.



> 
> 
> Experiences can *motivate* a decision, and hence an acceptance
> or a rejection of a statement, but a basic statement cannot be
> *justified* by them--no more than by thumping the table.
> (2002: 87-88)
> 
> 
> 



Statements can be justified only by other statements, and therefore
testing comes to an end, not in the establishment of a correlation
between propositional content and observable reality, as empiricism
would hold, but by means of the conventional, inter-subjective
acceptance of the truth of certain basic statements by the research
community.



The acceptance of basic statements is compared by Popper to trial by
jury: the verdict of the jury will be an agreement in accordance with
the prevailing legal code and on the basis of the evidence presented,
and is analogous to the acceptance of a basic statement by the
research community:



> 
> 
> By its decision, the jury accepts, by agreement, a statement about a
> factual occurrence--a basic statement, as it were. (2002: 92)
> 
> 
> 



The jury's verdict is conventional in arising out of a procedure
governed by clear rules, and is an application of the legal system as
a whole as it applies to the case in question. The verdict is
accordingly represented as a true statement of fact, but, as
miscarriages of justice demonstrate all too clearly,



> 
> 
> the statement need not be true merely because the jury has accepted
> it. This ... is acknowledged in the rule allowing a verdict to be
> quashed or revised. (2002: 92)
> 
> 
> 



This is comparable, he argues, to the case of basic statements: their
acceptance-as-true is also by agreement and, as such, it also
constitutes an application of a theoretical system, and



> 
> 
> it is only this application which makes any further applications of
> the theoretical system possible. (2002: 93)
> 
> 
> 



However, the agreed acceptance of basic statements, like that of
judicial verdicts, remain perennially susceptible to the requirement
for further interrogation. Popper terms this "the relativity of
basic statements" (2002: 86), which is reflective of the
provisional nature of the entire corpus of scientific knowledge
itself. Science does not, he maintains, rest upon any foundational
bedrock. Rather, the theoretical systems of science are akin to
buildings in swampy ground constructed with the support of piles:



> 
> 
> The piles are driven down from above into the swamp, but not down to
> any natural or "given" base; and if we stop driving the
> piles deeper, it is not because we have reached firm ground. We simply
> stop when we are satisfied that the piles are firm enough to carry the
> structure, at least for the time being. (2002: 94)
> 
> 
> 


## 5. The Growth of Human Knowledge



For Popper, the growth of human knowledge proceeds from our problems
and from our attempts to solve them. These attempts involve the
formulation of theories which must go beyond existing knowledge and
therefore require a leap of the imagination. For this reason, he
places special emphasis on the role played by the creative imagination
in theory formulation. The priority of *problems* in
Popper's account of science is paramount, and it is this which
leads him to characterise scientists as "problem-solvers".
Further, since the scientist begins with problems rather than with
observations or "bare facts", he argues that the only
logical technique which is an integral part of scientific method is
that of the deductive testing of theories which are not themselves the
product of any logical operation. In this deductive procedure
conclusions are inferred from a tentative hypothesis and are then
compared with one another and with other relevant statements to
determine whether they falsify or corroborate the hypothesis. Such
conclusions are not directly compared with the facts, Popper stresses,
simply because there are no "pure" facts available; all
observation-statements are theory-laden, and are as much a function of
purely subjective factors (interests, expectations, wishes, etc.) as
they are a function of what is objectively real.



How then does the deductive procedure work? Popper specifies four
steps (2002: 9):


1. The first is *formal*, a testing of the internal
consistency of the theoretical system to see if it involves any
contradictions.
2. The second step is *semi-formal*, "the investigation
of the logical form of the theory, with the object of determining
whether it has the character of an empirical or scientific theory, or
whether it is, for example, tautological" (2002: 9).
3. The third step is the comparing of the new theory with existing
ones to determine whether it constitutes an advance upon them. If its
explanatory success matches that of the existing theories, and it
additionally explains some hitherto anomalous phenomenon or solves
some hitherto unsolvable problems, it will be adopted as constituting
an advance upon the existing theories. In that sense, science involves
theoretical progress: on this account, a theory *X* is better
than a "rival" theory *Y* if *X* has
*greater empirical content*, and hence *greater predictive
power*, than *Y*.
4. The fourth and final step is the testing of a theory by the
empirical application of the conclusions derived from it. If such
conclusions are shown to be true, the theory is corroborated (but
never verified). If the conclusion is shown to be false, then this is
taken as a signal that the theory cannot be completely correct
(logically the theory is falsified), and the scientist begins his
quest for a better theory. He does not, however, *abandon* the
present theory until such time as he has a better one to substitute
for it.



The general picture of Popper's philosophy of science, then is
this: Hume's philosophy demonstrates that there is a
contradiction implicit in traditional empiricism, which holds that
universal scientific laws are in some way finally confirmable by
experience, despite the open-ended nature of the latter being
acknowledged. Popper eliminates the contradiction by removing the
demand for empirical verification in favour of empirical falsification
or corroboration. Scientific theories, for him, are not inductively
inferred from experience, nor is scientific experimentation carried
out with a view to verifying or finally establishing the truth of
theories; rather, *all knowledge is provisional, conjectural,
hypothetical*--the universal theories of science can never be
conclusively established. Hence Popper's emphasis on the
importance of the critical spirit to science--for him critical
thinking is the very essence of rationality. For it is only by
critical thought that we can eliminate false theories and determine
which of the remaining theories is the best available one, in the
sense of possessing the highest level of explanatory force and
predictive power.


## 6. Probability, Knowledge and Verisimilitude



In the view of many social scientists, the more probable a theory is,
the *better* it is, and if we have to choose between two
theories which differ only in that one is probable and the other is
improbable, then we should choose the former. Popper rejects this.
Science values theories with a high informative content, because they
possess a high predictive power and are consequently highly testable.
For that reason, the more *improbable* a theory is the better
it is scientifically, because the probability and informative content
of a theory vary inversely--the higher the informative content of
a theory the lower will be its probability. Thus, the statements which
are of special interest to science are those with a high informative
content and (consequentially) a low probability, which
*nevertheless come close to the truth*. Informative content,
which is in inverse proportion to probability, is in direct proportion
to testability. As a result, the severity of the test to which a
theory can be subjected, and by means of which it is falsified or
corroborated, is of fundamental importance.



Popper also argues that all scientific criticism must be piecemeal,
i.e., he holds that it is not possible to question every aspect of a
theory at once, as certain items of what he terms "background
knowledge" must be taken for granted. But that is *not*
knowledge in the sense of being conclusively established; it may be
challenged at any time, especially if it is suspected that its
uncritical acceptance may be responsible for difficulties which are
subsequently encountered.



How then can one be certain that one is questioning the right thing?
The Popperian answer is that we cannot have absolute certainty here,
but repeated tests usually show where the trouble lies. As we saw, for
Popper even observation statements are corrigible and open to review,
and science in his view is not a quest for certain knowledge, but an
evolutionary process in which hypotheses or conjectures are
imaginatively proposed and tested in order to explain facts or to
solve problems. For that reason, he emphasises both the importance of
questioning the background knowledge when the need arises, and the
significance of the fact that observation-statements are theory-laden
and corrigible.



Popper was initially uneasy with the concept of truth, and in his
earliest writings he avoided asserting that a theory which is
corroborated is true--for clearly if every theory is an
open-ended hypothesis, then *ipso facto* it has to be at least
potentially false. However, he came to accept Tarski's
reformulation of the correspondence theory of truth, and in
*Conjectures and Refutations* (1963) he integrates the concepts
of truth and content to frame the metalogical concept of
"truthlikeness" or "*verisimilitude*".
A "good" scientific theory, Popper argues in that work,
has a higher level of verisimilitude than its rivals, and he
explicates this concept by reference to the logical consequences of
theories. A theory's content is the totality of its logical
consequences, which can be divided into two classes:


1. the "*truth-content*", which is the class of
true propositions which may be derived from it, and
2. the "*falsity-content*" of a theory, which is
the class of the theory's false consequences (which may be
empty, and in the case of a theory which is true is necessarily
empty).



Popper offers two accounts of how rival theories can be compared in
terms of their levels of verisimilitude; these are the qualitative and
quantitative definitions. On the qualitative account, verisimilitude
is defined in terms of subclass relationships: a theory \(t\_2\) has a
higher level of verisimilitude than \(t\_1\) if and only if their
truth- and falsity-contents are comparable through subclass
relationships, and *either*


1. \(t\_2\)'s truth-content includes \(t\_1\)'s and
\(t\_2\)'s falsity-content, if it exists, is included in, or is
the same as, \(t\_1\)'s, or
2. \(t\_2\)'s truth-content includes or is the same as
\(t\_1\)'s and \(t\_2\)'s falsity-content, if it exists, is
included in \(t\_1\)'s.



On the quantitative account, verisimilitude is defined by assigning
quantities to contents, where the index of the content of a given
theory is its logical improbability, given again that content and
probability vary inversely (1963: 233-4). The utilisation of
either method of computing verisimilitude shows, Popper argues, that
even if a theory \(t\_2\) with a higher content than a rival theory
\(t\_1\) is subsequently falsified, it can still legitimately be
regarded as a better theory than \(t\_1\), and "better" is
here now understood to mean \(t\_2\) is *closer to the truth*
than \(t\_1\) (1963: 235).



Thus, scientific progress involves, on this view, the abandonment of
partially true, but falsified, theories, for theories with a higher
level of verisimilitude, i.e., which approach more closely to the
truth. In this way, verisimilitude allowed Popper to mitigate what
some saw as the pessimism of an anti-inductivist philosophy of
science. With the introduction of the concept, Popper was able to
represent his account as an essentially realistic position in terms of
which scientific progress can be seen as progress *towards* the
truth, and experimental corroboration can be viewed as an
*indicator* of verisimilitude.



However, subsequent research revealed defects in Popper's formal
definitions of verisimilitude. The concept is most important in his
system because of its application to theories which are approximations
(which are common in the social sciences) and thus known to be
*false*. In this connection, Popper had written:



> 
> 
> Ultimately, the idea of verisimilitude is most important in cases
> where we know that we have to work with theories which are *at
> best* approximations--that is to say, theories of which we
> know that they cannot be true... In these cases we can still
> speak of better or worse approximations to the truth (and we therefore
> do not need to interpret these cases in an instrumentalist sense).
> (1963: 235)
> 
> 
> 



In 1974, David Miller and Pavel Tichy, working independently,
demonstrated that the conditions specified by Popper in his accounts
of both qualitative and quantitative verisimilitude for comparing the
truth- and falsity-contents of theories can be satisfied only when the
theories are *true*. In the crucially important case of false
theories, Popper's definitions are formally defective: for with
regard to a false theory \(t\_2\) which has excess content over a rival
theory \(t\_1\), *both* the truth-content *and* the
falsity-content of \(t\_2\) will exceed that of \(t\_1\). With respect
to theories which are false then, Popper's conditions for
comparing levels of verisimilitude, whether in quantitative and
qualitative terms, can never be met.



Popper's response was two-fold. In the first place, he
acknowledges the deficiencies in his own formal account:



> 
> 
> "...my main mistake was the failure to see at once that my
> 'A Theorem on Truth-Content' [1966], could be extended to
> falsity content: if the content of a false statement *a*
> exceeds that of a statement *b*, then the truth content of
> *a* exceeds the truth content of *b*, and the same holds
> of their falsity contents." (1979, 371)
> 
> 
> 



But he argues that



> 
> 
> "I do think that we should not conclude from the failure of my
> attempts to solve the problem that the problem cannot be solved.
> Perhaps it cannot be solved by purely logical means but only by a
> relativization to relevant problems or even by bringing in the
> historical problem situation" (1979, 372).
> 
> 
> 



This suggestion was to precipitate a great deal of important technical
research in the field. He additionally moves the task of formally
defining the concept from centre-stage in his philosophy of science by
protesting that he had never intended to imply



> 
> 
> that degrees of verisimilitude ... can ever be numerically
> determined, except in certain limiting cases. (1979: 59)
> 
> 
> 



Instead, he argues, the chief value of the concept is heuristic, in
which the absence of an adequate formal definition is not an
insuperable impediment to its utilisation in the actual appraisal of
theories relativised to problems in which we have an interest.



Many see the thrust of this latter strategy as genuinely reflecting
the significance of the concept of verisimilitude in Popper's
system, but it has not satisfied all of his critics.


## 7. Objective Knowledge and The Three Worlds Ontology



Popper's hostility to psychologistic approaches to epistemology
is evident from his earliest works. Questions relating to the origins
of convictions, feelings of certainty and the like, he argues, are
properly considered the province of psychology; their attempted use in
epistemology, which has been characteristic in particular of some
schools of empiricism, can lead only to confusion and ultimately to
scepticism. Against it, he repeatedly insists on the objectivity of
scientific knowledge and sees it as the principal task of epistemology
to engage with the questions of justification and validity in that
connection (2002: 7).



In some of his later works in the field, particularly his
"Epistemology Without a Knowing Subject" (1967,
republished in *Objective Knowledge* [1972]) and in his lecture
"Three Worlds" in the Tanner Lectures on Human Values
delivered in 1978 (published 1980), Popper develops the notion of
objectivity further in a novel but controversial way by seeking to
free it completely from all psychological constraints. What is central
to epistemology, he reaffirms, is the concept of objectivity, which he
seeks to show requires neither the notions of subjective mental states
nor even that of a subject "possessing" knowledge:
knowledge in its full objective sense, he argues, is knowledge
"without a knowing subject".



Popper's angle of approach here is to situate the development of
knowledge in the context of animal and human evolution. It is
characteristic of evolutionary processes, he points out, that they
come to take place in an environment which is itself in part fashioned
by the species in question. Examples of this abound, such as the reefs
built by corals, the hives built by bees, the dams built by beavers
and the atmospheric effects yielded by plants. This, Popper contends,
is also true of human beings: we too have created new kinds of
products, "intellectual products", which shape our
environment. These are our myths, our ideas, our art works and our
scientific theories about the world in which we live. When placed in
an evolutionary context, he suggests, such products must be viewed
instrumentally, as exosomatic artefacts. Chief amongst them is
knowledge



> 
> 
> in the objective or impersonal sense, in which it may be said to be
> contained in a book; or stored in a library; or taught in a
> university. (1979: 286)
> 
> 
> 



On this view, termed "evolutionary epistemology", the
growth of human knowledge is an objective evolutionary process which
involves the creation and promulgation of new problem-solving
theories, which are then subjected to the challenge of criticism,
modification, elimination and replacement. These latter activities are
seen by Popper as growth-promoting in the evolution of knowledge,
which he represents by means of a tetradic schema (1979: 287):



\[ P\_1 \rightarrow \textit{TT} \rightarrow \textit{EE} \rightarrow P\_2. \]


Here "\(P\_1\)" stands for the "initial
problem"; "*TT*" stands for "tentative
theory" designed to solve it, "*EE*" stands
for "attempts at error-elimination", and
"\(P\_2\)" represents further problems that arise out of
the critical process.



This kind of knowledge development, Popper argues, cannot be explained
either by physicalism, which seeks to reduce all mental processes and
states to material ones, or by dualism, which usually seeks to
explicate knowledge by means of psychological categories such as
thought, perception and belief. Consequently, he proposes a novel form
of pluralistic realism, a "Three Worlds" ontology, which,
while accommodating both the world of physical states and processes
(world 1) and the mental world of psychological processes (world 2),
represents knowledge in its objective sense as belonging to world 3, a
third, objectively real ontological category. That world is the
world



> 
> 
> of the products of the human mind, such as languages; tales and
> stories and religious myths; scientific conjectures or theories, and
> mathematical constructions; songs and symphonies; paintings and
> sculptures. (1980: 144)
> 
> 
> 



In short, world 3 is the world of human cultural artifacts, which are
products of world 2 mental processes, usually instantiated in the
physical world 1 environment.



Popper proceeds to explicate his distinction between the subjective
and objective senses of knowledge by reference to this ontology. The
subjective sense of knowledge relates to psychological processes and
states, mental dispositions, beliefs and expectations, which may
generically be termed "thought processes" and which belong
to world 2. Knowledge in the objective sense, by contrast, consists
not of thought processes but of *thought contents*, that is to
say, the content of propositionalised theories: it is



> 
> 
> the content which can be, at least approximately, translated from one
> language into another. The objective thought content is that which
> remains invariant in a reasonably good translation. (1980: 156)
> 
> 
> 



And it is that thought content, when linguistically codified in texts,
works of art, log tables, mathematical formulae, which constitutes
world 3, to which objective knowledge relates.



For those who would suggest that such objects are mere abstractions
from world 2 thought processes, Popper counters that world 3 objects
are necessarily more than the thought processes which have led to
their creation. Theories, for example, usually have logical
implications beyond anything considered by their original author, as
instanced in the case of Einstein's Special Theory of
Relativity. Moreover, what is most characteristic about such objects
is that, unlike world 2 mental processes, they can stand in logical
relationships to each other, such as equivalence, deducibility and
compatibility, which makes them amenable to the kind of critical
rational analysis and development that is one of the hallmarks of
science. As he puts it,



> 
> 
> Criticism of world 3 objects is of the greatest importance, both in
> art and especially in science. Science can be said to be largely the
> result of the critical examination and selection of conjectures, of
> thought contents. (1980: 160)
> 
> 
> 



Popper takes Michelangelo's sculpture *The Dying Slave*
as an illustrative example of a world 3 object, embodied in a world 1
block of marble. Other examples given include memory engrams in the
brain, the American Constitution, Shakespeare's tragedies,
Beethoven's Fifth Symphony and Newton's theory of
gravitation. Each one of these, he contends, is a world 3 object that
transcends both its physical, world 1 embodiments and its world 2
cognitive origins (1980: 145).



Popper was aware that he would be accused of hypostatising
abstractions in asserting the reality and objectivity of world 3
objects. In response, he indicates strongly that he has no interest in
what he regards as pointless terminological disputes over the meaning
of the term "world" or "real". He is therefore
content, if required, to express his account of objective knowledge in
more familiar and perhaps more mundane terms: world 3 objects are
*abstract* objects while their physical embodiments are
*concrete* objects. But that should not be allowed to disguise
the fact that he saw the relationships between the three categories of
his ontology as of enormous importance in understanding the role of
science as an element of culture:



> 
> 
> my thesis is that our world 3 theories and our world 3 plans causally
> influence the physical objects of world 1; that they have a causal
> action upon world 1. (1980: 164)
> 
> 
> 



In the final analysis it is the causal interaction between the worlds
that ultimately matters in Popper's objectivist epistemology: it
allows him to represent the growth of human knowledge as an
evolutionary process of exosomatic adaptations, which is ultimately a
function of the interplay of relations between the physical and mental
worlds and the world of objective knowledge or thought content.


## 8. Social and Political Thought--The Critique of Historicism and Holism



Given Popper's personal history and background, it is hardly
surprising that he developed a deep and abiding interest in social and
political philosophy. He understood holism as the view that human
social groupings are greater than the sum of their members, that they
act on their human members and shape their destinies and that they are
subject to their own independent laws of development. Historicism he
identified as the belief that history develops inexorably and
necessarily according to certain principles or rules towards a
determinate end (as for example in the Marx's dialectical
materialism). The link between them is that holism holds that
individuals are essentially formed by the social groupings to which
they belong, while historicism suggests that we can understand such a
social grouping only in terms of the internal principles which
determine its development.



These lead to what Popper calls "The Historicist Doctrine of the
Social Sciences", the views (a) that the principal task of the
social sciences is to make predictions about the social and political
development of man, and (b) that the task of politics, once the key
predictions have been made, is, in Marx's words, to lessen the
"birth pangs" of future social and political developments.
Popper thinks that this view of the social sciences is both
theoretically misconceived and socially dangerous, as it can give rise
to totalitarianism and authoritarianism--to centralised
governmental control of the individual and the attempted imposition of
large-scale social planning. Against this, he advances the view that
any human social grouping is no more (or less) than the sum of its
individual members, that what happens in history is the (largely
unforeseeable) result of the actions of such individuals, and that
large scale social planning to an antecedently conceived blueprint is
inherently misconceived--and inevitably
disastrous--precisely because human actions have consequences
which cannot be foreseen. Popper, then, is an historical
*indeterminist*, insofar as he holds that history does not
evolve in accordance with intrinsic laws or principles, that in the
absence of such laws and principles unconditional prediction in the
social sciences is an impossibility, and that there is no such thing
as historical necessity.



The link between Popper's theory of knowledge and his social
philosophy is his fallibilism. We make theoretical progress in science
by subjecting our theories to critical scrutiny, and abandoning those
which have been falsified. So too in an open society the rights of the
individual to criticise administrative policies will be safeguarded
and upheld, undesirable policies will be eliminated in a manner
analogous to the elimination of falsified scientific theories, and
political differences will be resolved by critical discussion and
argument rather than by coercion. The open society as thus conceived
of by Popper may be defined as



> 
> 
> an association of free individuals respecting each other's
> rights within the framework of mutual protection supplied by the
> state, and achieving, through the making of responsible, rational
> decisions, a growing measure of humane and enlightened life. (R. B.
> Levinson 1953: 17)
> 
> 
> 



Such as society is not a utopian ideal, Popper argues, but an
empirically realised form of social organisation which is in every
respect superior to its (real or potential) totalitarian rivals. His
strategy, however, is not merely to engage in a moral defence of the
ideology of liberalism, but rather to show that totalitarianism is
typically based upon historicist and holist presuppositions, and of
demonstrating that these presuppositions are fundamentally
incoherent.


## 9. Scientific Knowledge, History, and Prediction



Historicism and holism, Popper argues, have their origins in what he
terms



> 
> 
> one of the oldest dreams of mankind--the dream of prophecy, the
> idea that we can know what the future has in store for us, and that we
> can profit from such knowledge by adjusting our policy to it. (1963:
> 338)
> 
> 
> 



This dream was given impetus, he suggests, by the emergence of a
genuine predictive capability regarding solar and lunar eclipses at an
early stage in human civilisation, which became refined with the
development of the natural sciences. Historicism derives a superficial
plausibility from the suggestion that, just as the application of the
laws of the natural sciences can lead to the prediction of such events
as eclipses, knowledge of "the laws of history" as yielded
by a social science or sciences can and should lead to the prediction
of future social phenomena. Why should we not conceive of a social
science which would function as the theoretical natural sciences
function and yield precise unconditional predictions in the
appropriate sphere of application? Popper seeks to show that this idea
is based upon a series of misconceptions about the nature of science,
and about the relationship between scientific laws and scientific
prediction.



In relation to the critically important concept of prediction, Popper
makes a distinction between what he terms "conditional
scientific predictions", which have the form "If
*X* takes place, then *Y* will take place", and
"unconditional scientific prophecies", which have the form
"*Y* will take place". Contrary to popular belief,
it is the former rather than the latter which are typical of the
natural sciences, which means that typically prediction in natural
science is conditional and limited in scope--it takes the form of
hypothetical assertions stating that certain specified changes will
come about if and only if particular specified events antecedently
take place. This is not to deny that "unconditional scientific
prophecies", such as the prediction of eclipses, for example, do
take place in science, and that the theoretical natural sciences make
them possible. However, Popper argues that (a) these unconditional
prophecies are not *characteristic* of the natural sciences,
and (b) that the mechanism whereby they occur, in the very limited way
in which they do, is not understood by the historicist.



What is the mechanism which makes "unconditional scientific
prophecies" possible? Popper's answer is that they are
possible because they are derived from a combination of conditional
predictions (themselves derived from scientific laws) *and*
existential statements specifying that the conditions in relation to
the system being investigated are fulfilled.



Given that this is the mechanism which generates unconditional
scientific prophecies, Popper makes two related claims about
historicism:



> 
> 
> The first is that the historicist does not, as a matter of fact,
> derive his historical prophecies from conditional scientific
> predictions. The second ... is that he cannot possibly do so
> because long term prophecies can be derived from scientific
> conditional predictions only if they apply to systems which can be
> described as well isolated, stationary, and recurrent. These systems
> are very rare in nature; and modern society is surely not one of them.
> (1963: 339)
> 
> 
> 



Popper accordingly argues that it is a fundamental mistake for the
historicist to take the unconditional scientific prophecies of
eclipses as being typical and characteristic of the predictions of
natural science; they are possible only because our solar system is a
stationary and repetitive system which is isolated from other such
systems by immense expanses of empty space. Human society and human
history are *not* isolated systems and are continually
undergoing rapid, non-repetitive development. In the most fundamental
sense possible, every event in human history is discrete, novel, quite
unique, and ontologically distinct from every other historical event.
For this reason, it is impossible in principle that unconditional
scientific prophecies could be made in relation to human
history--the idea that the successful unconditional prediction of
eclipses provides us with reasonable grounds for the hope of
successful unconditional prediction regarding the evolution of human
history turns out to be based upon a gross misconception. As Popper
succinctly concludes, "The fact that we predict eclipses does
not, therefore, provide a valid reason for expecting that we can
predict revolutions" (1963: 340).


## 10. Immutable Laws and Contingent Trends



An additional mistake which Popper discerns in historicism is the
failure of the historicist to distinguish between scientific
*laws* and *trends*. This makes him think it possible to
explain change by discovering trends running through past history, and
to anticipate and predict future occurrences on the basis of such
observations. Here Popper points out that there is a critical
difference between a trend and a scientific law: the latter is
universal in form, while a trend can be expressed only as a singular
existential statement. This logical difference is crucial: neither
conditional nor unconditional predictions can be based upon trends,
because trends may change or be reversed with a change in the
conditions which gave rise to them in the first instance. As Popper
puts it, there can be no doubt that



> 
> 
> the habit of confusing trends with laws, together with the intuitive
> observation of trends such as technical progress, inspired the central
> doctrines of ... historicism. (1957: 106)
> 
> 
> 



He does not, of course, dispute the existence of trends or deny that
observing them can be of practical utility value. But the essential
point is that a trend is something which *itself* ultimately
stands in need of scientific explanation, and it cannot therefore
function as the frame of reference in terms of which an unconditional
prediction can be based.



A point which connects with this has to do with the role which the
evolution of human knowledge has played in the historical development
of human society. Human history has, Popper points out, been strongly
influenced by *the growth of human knowledge*, and it is
extremely likely that this will continue to be the case--all the
empirical evidence suggests that the link between the two is
progressively consolidating. However, this gives rise to a further
problem for the historicist: no scientific predictor, human or
otherwise, can possibly predict its own future results. From this it
follows, he holds, that no society can predict, scientifically, its
own future states of knowledge. Thus, while the future evolution of
human history is extremely likely to be influenced by new developments
in human knowledge, we cannot now scientifically determine what such
knowledge will be.



From this it follows that if the future holds any new discoveries or
any new developments in the growth of our knowledge, then it is
impossible for us to predict them now, and it is therefore impossible
for us to predict the future development of human history now, given
that the latter will, at least in part, be determined by the future
growth of our knowledge. Thus, once again historicism
collapses--the dream of a theoretical, predictive science of
history is unrealisable, because it is an impossible dream.



Popper's argues against the propriety of large-scale planning of
social structures on the basis of this demonstration of the logical
shortcomings of historicism. It is, he argues, theoretically as well
as practically misguided, because, again, part of what we are planning
for is our future knowledge, and our future knowledge is not something
which we can in principle now possess--we cannot adequately plan
for unexpected advances in our future knowledge, or for the effects
which such advances will have upon society as a whole. For him, this
necessitates the acceptance of historical indeterminism as the only
philosophy of history which is commensurate with a proper
understanding of the provisional and incomplete nature of human
knowledge.



This critique of historicism and holism is balanced, on the positive
side, by Popper's affirmation of the ideals of individualism and
market economics and his strong defence of the open society--the
view that a society is equivalent to the sum of its members, that the
actions of the members of society serve to fashion and to shape it,
and that the social consequences of intentional actions are very
often, and very largely, unintentional. This part of his social
philosophy was influenced by the economist Friedrich Hayek, who worked
with him at the London School of Economics and who was a life-long
friend. Popper advocates what he (rather unfortunately) terms
"piecemeal social engineering" as the central mechanism
for social planning: in utilising this mechanism, intentional actions
are directed to the achievement of one specific goal at a time, which
makes it possible to determine whether adverse unintended effects of
intentional actions occur, in order to correct and readjust when this
proves necessary. This, of course, parallels precisely the critical
testing of theories in scientific investigation. This approach to
social planning (which is explicitly based upon the premise that we do
not, because we cannot, know what the future will be like) encourages
attempts to put right what is problematic in
society--generally-acknowledged social ills--rather than
attempts to impose some preconceived idea of the "good"
upon society as a whole. For Popper, in a genuinely open society
piecemeal social engineering goes hand-in-hand with *negative*
utilitarianism, the attempt to minimise the amount of suffering and
misery, rather than, as with positive utilitarianism, the attempt to
maximise the amount of happiness. The state, he holds, should concern
itself with the task of progressively formulating and implementing
policies designed to deal with the social problems which actually
confront it, with the goal of mitigating human misery and suffering to
the greatest possible degree. The positive task of increasing social
and personal happiness, by contrast, can and should be left to
individual citizens, who may, of course, act collectively to that end.
"My thesis", Popper states, is that



> 
> 
> human misery is the most urgent problem of a rational public policy
> and that happiness is not such a problem. The attainment of happiness
> should be left to our private endeavours. (1963: 361)
> 
> 
> 



Thus, for Popper, in the final analysis the activity of
problem-solving is as definitive of our humanity at the level of
social and political organisation as it is at the level of science,
and it is this key insight which unifies and integrates the broad
spectrum of his thought.


## 11. Critical Evaluation



While it cannot be said that Popper was modest, he took criticism of
his theories very seriously, and spent much of his time in his later
years in addressing them. The following is a summary of some of the
main ones which he had to address. (For Popper's responses to
critical commentary, see his "Replies to My Critics"
(1974) and his *Realism and the Aim of Science* (1983).



First, Popper claims to be a realist and rejects conventionalist and
instrumentalist accounts of science. But his account in the *Logic
of Scientific Discovery* of the role played by basic statements in
the methodology of falsification seems to sit uneasily with that. As
we have seen, he follows Kant in rejecting the positivist/empiricist
view that observation statements are incorrigible, and argues that
they are descriptions of what is observed as interpreted by the
observer with reference to a determinate conceptual and theoretical
framework. He accordingly asserts that while basic statements may have
a causal relationship to experience, they are neither determined nor
justified by it.



However, this would seem to pose a difficulty: if a theory is to be
genuinely testable, it must be possible to determine, at least in
principle, whether the basic statements which are its potential
falsifiers are actually true or false. But how can this be known, if
basic statements cannot be justified by experience? As we have seen,
Popper's answer is that the acceptance or rejection of basic
statements depends upon a convention-based decision on the part of the
scientific community.



> 
> 
> From a logical point of view, the testing of a theory depends upon
> basic statements whose acceptance or rejection, in its turn, depends
> upon our decisions. Thus it is decisions which settle the fate of
> theories. (2002: 91)
> 
> 
> 



Traditional conventionalism, as exemplified in the work of Mach,
Poincare and Milhaud amongst others, holds that a
"successful" science is one in which universal theories
have assumed such explanatory critical mass that a convention emerges
to pre-empt the possibility of their empirical refutation. This is
strongly rejected by Popper, who differentiates his position from it
by arguing that it is the acceptance of basic statements, rather than
that universal theory, which is determined by convention and
intersubjective agreement. For him, the acceptance or rejection of
theory occurs only indirectly and at a higher investigative level,
through critical tests made possible by the conventional acceptance of
basic statements. As he puts it, "I differ from the
conventionalist in holding that the statements decided by agreement
are not universal but singular" (2002: 92). Simultaneously,
however, he rejects any suggestion that basic statements are
justifiable by direct experience:



> 
> 
> I differ from the positivist in holding that basic statements are not
> justifiable by our immediate experiences, but are, from the logical
> point of view, accepted by an act, by a free decision. (2002: 92)
> 
> 
> 



It is thus evident that Popper saw his account of basic statements as
steering a course between the Scylla of orthodox conventionalism and
the Charybdis of positivism/empiricism. However, while it is both
coherent and consistent in that regard, there can be little doubt but
that it constitutes a form of conventionalism in its own right. And it
is not clear that it is compatible with scientific realism, understood
as the view that scientific theories give true or approximately true
descriptions of elements of a mind-independent world. As Lakatos puts
it,



> 
> 
> If a theory is falsified, it is proven false; if it is
> "falsified" [in Popper's conventionalist sense], it
> may still be true. If we follow up this sort of
> "falsification" by the actual "elimination" of
> a theory, we may well end up by eliminating a true, and accepting a
> false, theory. (Lakatos 1978: 24)
> 
> 
> 



Second, Popper's theory of demarcation hinges quite
fundamentally on the assumption that there are such things as critical
tests, which either falsify a theory, or give it a strong measure of
corroboration. Popper himself is fond of citing, as an example of such
a critical test, the resolution, by Adams and Leverrier, of the
problem which the anomalous orbit of Uranus posed for nineteenth
century astronomers. They independently came to the conclusion that,
assuming Newtonian mechanics to be precisely correct, the observed
divergence in the elliptical orbit of Uranus could be explained if the
existence of a seventh, as yet unobserved outer planet was posited.
Further, they were able, again within the framework of Newtonian
mechanics, to calculate the precise position of the "new"
planet. Thus when subsequent research by Galle at the Berlin
observatory revealed that such a planet (Neptune) did in fact exist,
and was situated precisely where Adams and Leverrier had calculated,
this was hailed as by all and sundry as a magnificent triumph for
Newtonian physics: in Popperian terms, Newton's theory had been
subjected to a critical test, and had passed with flying colours.



Yet Lakatos flatly denies that there are critical tests, in the
Popperian sense, in science, and argues the point convincingly by
turning the above example of an alleged critical test on its head.
What, he asks, would have happened if Galle had *not* found the
planet Neptune? Would Newtonian physics have been abandoned, or would
Newton's theory have been falsified? The answer is clearly not,
for Galle's failure could have been attributed to any number of
causes other than the falsity of Newtonian physics (e.g., the
interference of the earth's atmosphere with the telescope, the
existence of an asteroid belt which hides the new planet from the
earth, etc). The suggestion is that the
"falsification/corroboration" disjunction offered by
Popper is unjustifiable binary: non-corroboration is not necessarily
falsification, and falsification of a high-level scientific theory is
never brought about by an isolated observation or set of observations.
Such theories are, it is now widely accepted, highly resistant to
falsification; they are "tenaciously protected from refutation
by a vast 'protective belt' of auxiliary hypotheses"
(Lakatos 1978: 4) and so are falsified, if at all, not by Popperian
critical tests, but rather within the elaborate context of the
research programmes associated with them gradually grinding to a halt.
Popper's distinction between the logic of falsifiability and its
applied methodology does not in the end do full justice to the fact
that all high-level theories grow and live despite the existence of
anomalies (i.e., events/phenomena which are incompatible with them).
These, Lakatos suggests, are not usually taken by the working
scientist as an indication that the theory in question is false. On
the contrary, in the context of a progressive research programme he or
she will necessarily assume that the auxiliary hypotheses which are
associated with the theory can in time be modified to incorporate, and
thereby explain, recalcitrant phenomena.



Third, Popper's critique of Marxism has not, of course, gone
unchallenged. The debate arising from, however, has in many cases
tended to revolve around ideological rather than philosophical issues,
which will be passed over here. However, there have also been some
trenchant philosophical responses. Cornforth sees Marxism as a
rational scientific discipline and Marxian thinking as "a
rational and scientific approach to social problems" (Cornforth
1968: 6) of the kind which both Marx and Popper consider important.
Consequently, he takes Popper to task for representing Marxism as a
system of dogmas designed to close minds or pre-empt the operation of
our rational faculties in addressing social issues. Against that view,
he argues that it constitutes a way of thinking designed to open minds
to the real possibilities of human life, and sees it as the philosophy
best calculated to promote the ideals of the open society to which he,
like Popper, subscribes. Hudelson (1980) argues that Marxian economics
survives the Popperian critique of historicism and that, in any case,
Marx did not hold many of the tenets of historicism identified by
Popper. He also contends that Popper fails to show that there cannot
be, and that we cannot know, laws of social development and that Marx
did not in fact confuse trends and laws in the way that Popper
suggests.



Fourth, In the case of Freudian psychoanalysis, the adequacy of
Popper's critique has been challenged on philosophical grounds
by a number of commentators, particularly Adolf Grunbaum (1984).
Grunbaum is highly critical, indeed scornful, of Popper's
dismissal of the claims of psychoanalysis to be scientific and argues
that Freud showed "a keen appreciation of methodological
pitfalls that are commonly laid at his door by critics"
(Grunbaum 1984: 168) such as Popper. He argues that Freud was
sensitive to the question of the logic of the confirmation and
disconfirmation of psychoanalytic interpretations and cites
Freud's use of the concept of consilience, the convergence of
evidence from disparate sources, as a serious and explicit attempt to
meet the requirements of that logic. For Grunbaum, Popper's
critique of Freud amounts a veritable parody of the pioneering thinker
who established the discipline of psychoanalysis, and he attributes
that to Popper's "obliviousness to Freud's actual
writings" (1984: 124). He points out, for example, that the case
of the drowning child which Popper uses in *Conjectures and
Refutations* (Popper 1963: 35), upon which he rests part of his
case against psychoanalysis, is contrived and not in any way derived
from Freud's actual clinical texts.



Grunbaum contends that there are instances in Freud's
writings where he shows himself to be "a sophisticated
scientific methodologist" (Grunbaum 1984: 128), keenly
aware of the need for his theoretical system to meet the requirement
of testability. One such occurs when Freud, in his assessment that
anxiety neuroses are due to disturbances in sexual life, explicitly
refers to the notion of falsifiability: "My theory can only be
refuted when I have been shown phobias where sexual life is
normal" (Freud 1895 [1962: 134]). Another occurs in
Freud's 1915 paper "A Case of Paranoia Running Counter to
the Psycho-Analytic Theory of the Disease", in which, as the
title suggests, he saw the patient's collection of symptoms as
potentially falsifying the theory. Moreover, Freud's entire
account of paranoia as being due to an underlying repressed
homosexuality is open to empirical refutation, Grunbaum argues,
since it has the testable implication that a reduction in rates of
paranoia should result from a removal or loosening of social sanctions
against same-sex relationships (1984: 111).



Grunbaum accordingly holds that Freudian theory should be
considered falsifiable and therefore genuinely
scientific--albeit, in his view, ultimately unsuccessful, because
the clinical evidence offered in its favour is contaminated by
suggestion on the part of the analyst and cannot therefore support its
conceptual weight. That is a verdict very different to what
Grunbaum sees as the reductive dismissal of Freud offered by
Popper: "the inability of certain philosophers of science to
have discerned any testable consequences of Freud's
theory", he concludes, "betokens their insufficient
command or scrutiny of its logical content rather than a scientific
liability of psychoanalysis" (1984: 113).



There can be little doubt of the seriousness of this challenge to
Popper's critique of the claims of psychoanalytic theory to
scientific status. Further, the unparalleled cultural impact of
Freudianism upon contemporary life can scarcely be denied, and even a
cursory examination of the vast corpus of Freud's works reveals
a thinker of quite extraordinary theoretical power and imagination
whose claims to scientific validity cannot be dismissed lightly.



However, while the detail of this psychoanalytic response to Popper is
contestable, what is perhaps most striking and important about it is
that, as articulated by Grunbaum, it is itself couched in broad
terms of an acceptance of a Popperian account of science. That is to
say, in rejecting the claim that psychoanalysis fails to meet the
standard of falsifiability specified by Popper,
Grunbaum--who also rejects the hermeneutic interpretation of
Freud offered by thinkers such as Paul Ricoeur and Jurgen
Habermas--nonetheless implicitly accepts that very standard, and
with it the broad sweep of Popper's theory of demarcation. For
that reason alone, it seems clear that Popper's work will
continue to function as a critical reference point in the ongoing
debate regarding the scientific status of Freudian thought.



Fifth, scientific laws are usually expressed by universal statements
(i.e., they take the logical form "All *A*s are
*X*", or some equivalent) which are therefore concealed
conditionals--they have to be understood as hypothetical
statements asserting what would be the case under certain ideal
conditions. In themselves they are not existential in nature. Thus
"All *A*s are *X*" means "If anything
is an *A*, then it is *X*". Since scientific laws
are non-existential in nature, they logically cannot in themselves
imply any basic statements, since the latter are explicitly
existential. The question arises, then, as to how any basic statement
can falsify a scientific law, given that basic statements are not
deducible from scientific laws in themselves? Popper answers that
scientific laws are always taken in conjunction with statements
outlining the "initial conditions" of the system under
investigation; these latter, which are singular existential
statements, yield hard and fast implications when combined with the
scientific law.



This reply is adequate only if it is true, as Popper assumes, that
singular existential statements will always do the work of bridging
the gap between a universal theory and a prediction. Hilary Putnam in
particular has argued that this assumption is false, in that in some
cases at least the statements required to bridge this gap (which he
calls "auxiliary hypotheses") are general rather than
particular, and consequently that when the prediction turns out to be
false we have no way of knowing whether this is due to the falsity of
the scientific law or the falsity of the auxiliary hypotheses. The
working scientist, Putnam argues (Putnam 1974; see also the 1991
reprinting with its retrospective note), always initially assumes that
it is the latter, which shows not only that, but also why, scientific
laws are, *contra* Popper, highly resistant to falsification,
as Kuhn (1962) and Lakatos (1970, 1978) have also argued.



Popper's final position is that he acknowledges that it is
impossible to discriminate science from non-science on the basis of
the falsifiability of the scientific statements alone; he recognises
that scientific theories are predictive, and consequently prohibitive,
only when taken in conjunction with auxiliary hypotheses, and he also
recognises that readjustment or modification of the latter is an
integral part of scientific practice. Hence his final concern is to
outline conditions which indicate when such modification is genuinely
scientific, and when it is merely *ad hoc*. This is itself
clearly a major alteration in his position, and arguably represents a
substantial retraction on his part: Marxism can no longer be dismissed
as "unscientific" simply because its advocates preserved
the theory from falsification by modifying it--for in general
terms, such a procedure, it transpires, is perfectly respectable
scientific practice. It is now condemned as unscientific by Popper
because the only rationale for the modifications which were made to
the original theory was to ensure that it evaded falsification, and so
such modifications were *ad hoc*, rather than scientific. This
contention--though not at all implausible--has, to hostile
eyes, a somewhat contrived air about it, and is unlikely to worry the
convinced Marxist. On the other hand, the shift in Popper's own
basic position is taken by some critics as an indicator that
falsificationism, for all its apparent merits, fares no better in the
final analysis than verificationism.