## 1. Life



Sylvan was born in 1935 in Levin, New Zealand. He received his MA in
Philosophy from the University of New Zealand (Wellington) in 1957 and
the following year completed a first-class Honours degree in
mathematics there. His MA thesis, a 385-page work entitled *Moral
Scepticism* was given a mark of 95% by Arthur Prior, though he
later commented that this was "not so much a mark as an
exclamation mark" (quoted in D. Hyde, Introduction to Eckert
(ed.) 2018, xiv). Blackwell agreed to publish a condensed version of
the thesis but the required revisions were never undertaken.



In 1959, his teacher George Hughes then employed Sylvan to build a
small electro-mechanical computer capable of determining whether input
formulae were logical truths, logical falsehoods, or
neither--with green, red and amber lights displaying the
respective outcomes. He worked out how to build it from scratch using
relays and uniselectors discarded by the post office and it was a
success, but when run some years later it drew so much power that it
blacked out the building it was housed in, ruining several experiments
in biology running in the building at the time. The Biology Department
insisted that it never be used again (Hyde 2014, 43).



In mid-1959, while bushwalking in Australia, he met Jack Smart (then
in Adelaide, later a colleague at the Australian National University
and good bushwalking friend thereafter) who encouraged him to go to
Princeton for graduate work, as opposed to the then more usual choice
of UK universities like Cambridge. At Smart's urging, "as
a brash young man" Sylvan travelled to Princeton with a
Fulbright scholarship for doctoral studies under Alonzo Church to
"repair and renovate a derelict philosophy of science"
(Sylvan 2000a, 7). After two and a half years he was awarded an MA
from Princeton University but left before completing his PhD,
dissatisfied with the intellectual climate there and subsequent lack
of progress on his project. (He later received a PhD from Princeton in
1980 for chapter one of Routley 1980.) He accepted a lectureship at
Sydney University in 1962 where he began lecturing undergraduates in
logic--introducing modern Russellian theory, displacing John
Anderson's long insistence on Aristotelian theory. There he met
Val Plumwood (then Val Macrae, later Val Routley) and, in 1964, they
moved to the University of New England where Sylvan joined Len Goddard
and a growing department--the first to have begun teaching modern
logic in Australia under Goddard in 1957. Goddard and Sylvan founded
the first Australian Masters program in logic and formed the
*Australasian Association of Logic*, and with Len Goddard,
David Londey, Ross Brady, Malcolm Rennie and Val Plumwood, he
developed what became known as the New England Group--working on
non-classical logic and paradoxes, among other things--but
Goddard left a few years later, returning to St Andrews in Scotland.
In 1967, with a year's sabbatical owing, Sylvan and Plumwood
married (with Plumwood taking the name Routley) and they drove from
the University to St Andrews to continue work with Goddard (traversing
northern Australia, shipping the car from Darwin to Singapore, then
overland into India and Pakistan, through the Middle East and Eastern
Europe). Upon return, in 1968, Sylvan took a position at Monash
University before being appointed to a Senior Fellowship in Philosophy
in the Research School of Social Sciences at the Australian National
University (ANU) in 1971, where he remained for the rest of his
career. With only postgraduate students to supervise, his days
teaching undergraduates was at an end. A number of researchers from
the New England Group subsequently joined him there and, with the
addition of Bob Meyer, Graham Priest, and others, a group re-formed
around Sylvan at the ANU--the well-known Canberra Logic Group
that went on to pioneering research in non-classical, especially
relevant, logic. Through his contribution to the formation of research
groups that were both innovative and productive, Sylvan influenced a
whole generation of Australian philosophers and logicians. (For more
on this history of modern logic in Australia, cf. Routley 1984c,
Goddard 1992, and Brady and Mortensen 2014.)



The natural world also fascinated Sylvan. By the time of his death he
had purchased, and worked to conserve, five large tracts of rich
forest areas--four of which were subsequently bequeathed for
conservation.



> 
> 
> He took such a delight in nature, not so much the delight that a
> romantic might take in the overall beauty of it all, but a delight in
> its richness and complexity, in the detail that he found in the
> structure of mosses and in the behaviour of insects. ...
> It's as if in a strange way he was part of it .... (quoted
> in D. Hyde, Introduction to Eckert (ed.) 2018, xxv).
> 
> 
> 



Within a year of arriving at the ANU (the centre of Australian
forestry policy development), he and Plumwood became aware of plans
for extensive clearing of "useless" native forest for pine
plantations across the country and so began work on a sustained
critique of Australian forestry practices (Routley and Routley 1973a)
alongside joint work rethinking issues in environmental philosophy.
The critical and "pugilistic" style of the book caused an
uproar in forestry--with an attempt to suppress its publication
(cf. Routley and Plumwood 1986). The repressive nature of the
Australian forestry industry was widely understood from within, with
one forestry insider commenting, on receipt of a letter from Sylvan
early in the project, that: "for an Australian forester,
receiving a letter from you is somewhat akin to a new Party member
getting a birthday card from Alexander Solzhenitsyn" (Sylvan
RSC, Box #45). Closer to home, they were also criticised by some
colleagues who, in the days before applied philosophy had come of age,
saw their work as "propaganda" rather than scholarly
research. Despite resistance though, the book's successful
publication helped reform forestry in Australia, being subsequently
described by a leading forestry expert as "monumentally
important" and "the most incisive and devastating economic
analysis of forestry ... ever done in Australia" (Byron
1999, 53). All three editions published through the ANU Press between
1973 and 1975 sold out but by 1975 Sylvan was, remarkably, banned from
using the ANU's Forestry Department Library (the central store
for documents relating to the development of national forestry policy)
and further, planned editions were effectively stopped.



In 1975, Sylvan and Plumwood realised their dream of moving "off
grid" into the temperate rainforest in the coastal ranges east
of Canberra where they began building a house from local stone (one of
five houses that Sylvan built over his life). Working first from a
tent, then a shed, over the subsequent five years it took to build the
house they produced much of their key work on relevant logic,
neo-Meinongian metaphysics and environmental philosophy--often
discussing philosophy while building with graduate students and guests
who could be roped in to help. After a productive twenty-year
partnership, Sylvan and Plumwood parted ways in 1983, and he married
Louise Sylvan (nee Merlin). That was also the year he changed
his name from 'Richard Routley' to 'Richard
Sylvan' while Val Routley, as she was then known, became Val
Plumwood. Sylvan and Plumwood continued to work and correspond on
closely related themes in environmental philosophy until
Sylvan's death in 1996.



While his students and research assistants found him supportive and
kind, Sylvan's style sometimes offended his peers. He could be
very blunt in his assessment of other's arguments and his shy
demeanour and lack of small talk did little to counteract feelings of
rude-dismissal--friend and colleague Bob Meyer commenting that he
"was a difficult man; not only did he fail to suffer fools
gladly, but he often disdained suffering them at all" (Meyer
1996). Sylvan himself also commented, for example, that his
"Critique of Deep Ecology" (Sylvan 1985) would "risk
offending many friends in the deeper ecology movement" (i) and,
while he remained good friends with chief target Arne Naess, some
were, no doubt, offended. It earned him the title 'the bad boy
of deep ecology' (Orton 2005, Other Internet
Resources)--still considered a "deep ecologist"
despite the substance of his criticism concluding in his rejecting
deep ecology in favour of what he termed "deep green
theory". Some who took offense on reading his response to their
work would later go on to befriend and work with Sylvan, having gotten
past his blunt exterior. But with opposing-authority there was rarely
any rapprochement; his anti-authoritarianism was deep-rooted and his
anarchist tendencies manifest--in both academic work and in his
behaviour.



His publishing habits also drew attention. Seeking an outlet for
longer papers and essays in the late 1970s, and wary of
"profiteering" publishers, in the do-it-yourself spirit
that infused much of Sylvan's life he began publishing a number
of pre-print series in the Research School of Social Sciences where he
worked at the ANU. Beginning with work of the Canberra Logic Group,
the "Yellow Series" (as it became known) included over
twenty publications by Group members between 1978 and 1985. There
followed other Series including work in logic, metaphysics, the
philosophy of science and much of his own work in environmental
philosophy. In total, there were over fifty such publications of which
over half were Sylvan's own work. The publications ranged from
tens of pages to hundreds and could be purchased by post from the
department for a few dollars. The largest, at just over one thousand
pages (*Exploring Meinong's Jungle and Beyond*), for
example, was available in hardback for $10. Such anomalous publishing
habits meant that a considerable amount of his work is now very hard
to access (though, in some cases, republication through more usual
channels is underway--e.g., Eckert (ed.) 2018; Hyde (ed.) 2019;
and Weber (ed.) 2019).



He died in June 1996 aged 60, while entering a sacred temple in Bali
to discuss Hindu philosophy with priests there. (For more details, see
Hyde 2014.)


## 2. Logic



This section describes Sylvan's work in logic. As in other areas
of his philosophy, Sylvan was notable for his staunch defence of
highly controversial and radical views--most strikingly, that
classical logic is wrong, that non-classical logic is right, and that
some contradictions may be *true* (see: dialetheism). What
makes his work worth remembering is that he backed up such claims with
rigorous (if contentious) arguments and mathematical details.



Sylvan's work in logic can be viewed in part as a response to a
wide range of *paradoxes*, such as the paradoxes of
self-reference (like the Liar Paradox). He was equally focused on
*paradoxes of implication*, and so was a leading developer of
*relevant logics*, logics characterized by their concern that
there be a meaningful connection between the antecedent and consequent
of a conditional. These topics would lead him to be one of the
founders of the so-called "Australasian school" of
*paraconsistent logic*, logics that tolerate inconsistency
without incoherence (Hyde 2014, 71 and see the entry on 
 paraconsistent logic). 
 He was perennially concerned with the
*universality* of logic. Along with intrinsic interest, his
logical research was always motivated by its eventual application to
issues in metaphysics, ethics, and beyond.


### 2.1 Early work



This section describes Sylvan's work in neutral quantification
theory and significance logics. In both cases, he is concerned with
granting legitimacy to otherwise discredited or rejected
entities--the existence (or lack thereof) of objects that seem
like perfectly good subjects of quantification in apparently true
sentences; and the status of "nonsensical" sentences that
seem like they are essential parts of good reasoning.


#### 2.1.1 Quantification



From his earliest days at Princeton, Sylvan had argued that an
adequate philosophy of science required quantification over
non-existent objects (numbers, frictionless planes, etc.), and an
adequate semantics for fictional discourse was also best pursued along
these lines. (Cf. Routley 1965, 1966a, 1979a; Routley and Routley
1973b, 1979a.) For reasons discussed in Section 3 below, he followed
Meinong in seeking a theory that includes non-existent objects, and a
logic that can handle such objects.



A basic idea here (e.g., in Routley 1980) is to reassess the status of
the *existential quantifier*: \(\exists\). It is commonplace
amongst logicians, especially since Russell 1905 and especially
Quine's article "On What There Is", to read this as
*ontologically loaded*; so if \(\exists x Ax\) is true then
some \(x\) exists and has property \(A\). Sylvan urges that we
distinguish between *particular* claims ('some \(x\) is
\(A\)') and *existential* claims ('an
*existing* \(x\) is \(A\)'). With the latter existential
reading, it is impossible to claim that some things just do not exist;
that amounts to saying something both exists and does not exist, so it
exists after all. But with the former *particular* reading, the
claim 'some things do not exist' comes out as intended,
with its apparent natural language meaning. Because the existential
interpretation of the backward 'E' symbol has become
hopelessly entrenched, Sylvan introduced new symbols, 'P'
(for particular) and its dual 'U' (universal), to act as
*neutral* quantifiers. Thus the logical ground was laid for
subsequent work in neo-Meinongian metaphysics (cf. Section 3).



This work, both the metaphysics and logic, led to a number of debates
with David Lewis. Lewis (1990) argues that the apparently deep
disagreement Sylvan has with ontologically loaded quantification might
be dispelled by a translation manual, between his unconventional
Meinongian reading and a conventional one (cf. Priest 2005, Section
7.9.):



> 
> * when [Sylvan] says 'is an object' this can be replaced
> by 'exists';
> * when [Sylvan] says 'exists' this can be replaced by
> 'is a concrete object'
> 
> 
> 



If this is right, then it appears Sylvan is in danger of doing little
more than quibbling about the use of the word 'exists'
when it comes to abstract objects. But Lewis is self-critically aware
that any misunderstanding may be mutual, and cautions that



> 
> 
> To suppose that [Sylvan] mistakes mere terminological difference for
> profound philosophical disagreement is to accuse him of stupidity far
> beyond belief (Lewis 1990, 30).
> 
> 
> 



Worry about communication difficulties between classical and
non-classical logicians would be voiced by Lewis again, eventually
declining to debate at all (Lewis 1999, and cf. Smart 1977).


#### 2.1.2 Significance



With the formation of the New England Logic Group, we find the first
instances of Sylvan pursuing the development of *non-classical
logics* as a response to a range of paradoxes. A preliminary
aspect to this work was the investigation of the fundamental notion of
*significance*.



Especially in early 20th century philosophy, a popular
means of dismissing various philosophical theses (say in metaphysics)
was "on the grounds that they are nonsense, nonsignificant,
absurd, meaningless, unintelligible, or logically odd" (Goddard
and Routley 1973, 1). Such rejections are characteristic of logical
positivism, taking a cue from Wittgenstein's accusation that
much of philosophy is "not false, but senseless
[*unsinnig*]" [*Tractatus* 4.003] and therefore
easy to ignore. By the late 1960s, it seemed to Routley and Goddard
that Russell and others had succeeded in promoting a
"meaninglessness" solution to various paradoxes like the
Liar sentence, or the Russell contradiction,



> 
> 
> the set \(R\) of all sets that are not members of themselves is a
> member of itself if and only if it is not a member of itself
> 
> 
> 



According to various Russell/Tarski type theories, sentences are
regimented to levels of a hierarchy and restricted in scope about what
they can express; then liar-type sentences are, on this sort of
solution, "nonsense". Appeal to non-significance is then
meant to avoid paradox. (As Goddard and Routley put it, "Russell's solution [to his paradox] was to claim that the premisses of the argument are meaningless. In this way the paradox is stopped and the inconsistency removed. For the argument can no longer be stated and the contradictory conclusion no longer follows. The argument evaporates" (2).) Goddard and Routley are concerned that
philosophers have been too eager to condemn theses that "are
neither gibberish nor ungrammatical" (4).



In response, Routley (1966b), Brady and Routley (1973), and Goddard
and Routley (1973) argue for a logic of significance for the formal
study of significance. The ideas here can be summed up in three
theses. *First*, there are grammatically correct natural
language sentences, containing only recognized vocabulary (say of
English), which "are held to be meaningless" (Goddard and
Routley 1973, 2); but "unlike seriously ungrammatical sentences,
[they] can figure in valid arguments and can occur as unquoted
components of grammatical sentences" (Routley 1969, 367).
*Second*, such sentences require a non-classical and
specifically *three-valued* logic. Meaningless sentences still
must have some recognized *status*--and it is some status
other than 'true' or 'false' (See Haack 1971,
1975, and Bradley 1978 for alternatives). As Brady and Sylvan put
it,



> 
> 
> We believe that the deep structure of natural languages, and hence of
> the languages in which philosophical problems are characteristically
> formulated, will have to be based on an enriched significance logic
> which has a third value--nonsense or nonsignificance--and
> not on a classical two-valued logic which only has truth and falsity
> as its values (Brady and Routley 1973, 211).
> 
> 
> 



*Third*, all significance logics will need to be based on a
common *context logic*, where a fixed context of use or
circumstance determines the 'significance principles' of
each logic (Cocchiarella 1984; cf. Ripley 2012, 101).



Sylvan and Goddard want a logic that can track (as opposed to simply
deny) non-significant sentences, which we may think of as
*truth-value gaps*. Their proposed logic of significance may be
understood (see Szmuc and Omori 2018) as being based on a three-valued
logic, *weak Kleene*, given by the following truth tables:





\[\begin{array}{c|c}
& \neg \\
 \hline t & f \\
 \hline n & n \\
 \hline f & t 
\end{array}\]




\[\begin{array}{c|c|c|c}
\land & t & n & f \\
 \hline t & t & n & f \\
 \hline n & n & n & n \\
 \hline f & f & n & f 
\end{array}\]




\[\begin{array}{c|c|c|c}
\lor & t & n & f \\
 \hline t & t & n & t \\
 \hline n & n & n & n \\
 \hline f & t & n & f 
\end{array}\]




The intermediate value, \(n\) (for 'nonsense'), is to be
read as, not a truth-value, but rather as a kind of meaninglessness.
These matrices respect two basic conditions laid down in (Goddard and
Routley 1973, 260), that


* in the case of classical truth values \(t\) and \(f\), the tables
just are those of classical logic, so that this is a generalization of
the classical case
* any sentence with a non-significant component itself becomes
non-significant



An argument is *valid* on this logic iff there is no evaluation
that interprets all the premises as true (value \(t\)) but the
conclusion untrue (values \(f\) and \(n\)). This logic was further
investigated by Brady (1980) and Bunder (1979, 1980a, 1980b). For
criticism, see Lambert (1968) and Haack (1971, 1975).



This early work is transitional. Paradoxical sentences at this stage
of Sylvan's thinking may have a value, but certainly not that of
'true' (or 'false'). This relatively
conservative attitude would begin to fall away as his thinking
developed.


### 2.2 Relevant and Paraconsistent Logic



This section describes Sylvan's work as part of the Canberra
Logic Group's pioneering research on relevant and paraconsistent
logics, and applications to naive set theory. In the mid-1970s,
Routley/Sylvan produced a closely interconnected body of work (1975;
Routley and Meyer 1976, 1977, 1979; Routley *et al.* 1982),
much of it in collaboration with Val Plumwood (then Routley), Meyer,
Brady, and Priest (e.g., Priest and Routley 1983), circling around a
few key ideas, the germs of which we have already met: universality;
implication and entailment; and inconsistency. We now visit these in
turn.


#### 2.2.1 Universality



In 1975 Sylvan took up the idea of a *universal semantics*
directly (although the title of his paper "Universal
Semantics?" is in the uncertain form of a question). Inspired by
recent advances in Montague grammar and categorial languages, he
became speculatively interested in whether there is some common form
beneath all natural languages, that could be adequately represented
though logical symbolism. Specifically, he was interested in some
"leading assumptions" of the time, namely (1975, 327):


1. that the surface structure of a grammar can be transformed, or
translated, or reduced, into a "deep structure"; and
2. that the semantics of the deep structure is (some complication of)
a two-valued possible worlds semantics.



Here we can see two recurring concerns in Sylvan's logical work:
a sceptical interest in the idea of a model-theoretic reduction (to be
lambasted most vociferously with Meyer in their paper
"Extensional Reduction" of 1977), and the uses of worlds
semantics to do it.



As an initial gloss, a *universal* semantics, whatever else it
may be, is intended to be a framework able to express everything that
can be expressed. As in Section 2.1, there should not be any
artificial constraints placed on what we might be able to reason well
about (or, by extension, think about or imagine), nonsense or not. And
a universal logic should *not* have, as theorems, anything that
is patently incorrect. Putting these two ideas together, Sylvan was
already convinced that "classical logic" is too strong to
serve as the basis for any universal semantics, because it
*cannot* express everything that is expressible, such as many
intensional notions; and it *does* deliver apparently
nonsensical theses such as the paradoxes of material implication (see
Section 2.2.2 below). (These two aspects of a logic--the extent
of the class of models it can describe, and the set of validities it
yields--are inversely proportional; cf. Priest 2008,
36-7.)



On these grounds, Sylvan looked increasingly at non-classical logics
as a better framework or foundation for any universal semantics. His
1977 manifesto "Ultralogic as universal?" (see Ficara
2023) introduces the titular subject (note again the question mark) as
follows:



> 
> 
> A universal logic, in the intended sense, is one which is applicable
> in every situation whether realised or not, possible or not. Thus a
> universal logic is like a universal key, which opens, if rightly
> operated, all locks. It provides a canon for reasoning in every
> situation, including illogical, inconsistent and paradoxical ones. Few
> prevailing logics stand up to such a test. ... [A] universal
> logic should be adequate for mathematical *and* philosophical
> purposes--and also for logical functions in other areas such as
> biology, economics, astrology, theology, and so on (893).
> 
> 
> 



Approaching any universal logic, according to Sylvan, would require
extending the expressive power of classical logic, and concomitantly
restricting its proving power.



Two possible misinterpretations of this "universalist"
project should be flagged. First, Sylvan did not argue that some
specific alternative logic is the absolutely correct one, or even that
there should be one and only one correct alternative (see Section
3.3). Second, although he can sound rhetorically partisan and
ideological, Sylvan's approach was ultimately rather pragmatic:
he couched theory choice in practical cost/benefit analyses familiar
from conventional philosophy of science (Routley 1980a). On the
meaning of 'universality' in this context see Mares (2019)
and Nolan (2018). Brady's 2006 book takes its title in part from
Sylvan's announced project, with a focus on logics for
"meaning containment".


#### 2.2.2 Implication



Faced with the limitations of classical logic, Sylvan joined in the
project of refining C.I. Lewis's *strict implication* to
overcome various paradoxes of the conditional. (See the encyclopedia
entry on 
 indicative conditionals.) 
 For, according to the classical
account of material implication \(\supset\), for any three random
declarative sentences \(p\), \(q\), \(r\) you find on the Internet, \(
(p \supset q) \lor (q \supset r) \) is valid (to take just one
example; see Routley *et al.* 1982, 6-7). One diagnosis
of the problem here is that all these conditionals, of the form
'if \(p\) then \(q\)', display *irrelevance*: the
antecedent \(p\) need not have anything "to do with" the
consequent \(q\), whereas correct natural language conditionals (so
the argument goes) always respect some kind of relevant connection.
The problem may be resolved by turning to an appropriate relevant
logic. (See the related entry on 
 relevance logic.)



Sylvan is explicit, though, that his "main concern is not really
relevance at all--the appropriate sort of relevance is a
by-product of any good implication relation, which comes out in the
wash" (Routley *et al.* 1982, x) after a deeper diagnosis
of the paradoxes. He emphasizes that what is really at issue for a
successful account of a conditional is *absolute
sufficiency*--that when \(p\) really does imply \(q\), this
means that \(p\) is all that is needed for \(q\).



> 
> 
> The central deducibility relation of ultramodal logics, entailment, is
> intended to capture the notion of sufficiency ... of the
> antecedent of an entailment on its own, without any additional
> imported truth, especially imported logical truths. ...
> Sufficiency is a go-anywhere notion, which is not limited by the fact
> that the situation in which it operates is somehow classically
> incoherent, e.g., inconsistent or paradoxical. If \(A\) is sufficient
> for \(B\) then it does not matter what else goes on; logical laws may
> go haywire but nothing subtracts from \(A\)'s sufficiency (1977,
> 896).
> 
> 
> 



So while Sylvan's contribution to relevant logic was seminal,
his concerns diverged from some other "relevantists", such as Anderson and Belnap (1975). In
some otherwise highly critical remarks, Burgess (1983, 45) writes that
"Routleyanism and Andersonianobelnapianism are so dissimilar
that it is misleading to apply a single label
'relevantism' to both. (And indeed, [Sylvan] sometimes
adopts a different label.)"



The diagnosis of the paradoxes of implication as failures of respect
for sufficiency leads naturally to an alternative path to their
resolution, of a piece with Sylvan's concerns about
universality. On this view, the paradoxes of implication are symptoms
of taking *too few* possibilities into account. One may think
of classical material implication as taking only *one*
situation into account, giving rise to theorems like 'if \(p\)
then \(q\), or if \(q\) then \(p\)', since either \(p\) is true
(in which case, \(p\) or \(\twiddle q\) is true, and so *q*
materially implies \(p\)) or else \(p\) is false (in which case,
\(\twiddle p\) or \(q\) is true, and so \(p\) materially implies
\(q\)). This is immediately resolved upon consideration of
*two* possibilities, \(w\_0\) and \(w\_1\),





\[\begin{array}{c}
w\_0 \\
 p, \twiddle q \\
 
\end{array}\]




\[\begin{array}{c}
w\_1 \\
 \twiddle p, q 
\end{array}\]




and thinking of 'if \(p\) then \(q\)' as meaning that in
*every* world in which \(p\), also \(q\), i.e.,

 
\[ p \rightarrow q := \mathit{necessarily}, p \supset q \]


Then '\(p \rightarrow q, \mathrm{or}\, q \rightarrow p\)'
has a counterexample, points at which *p* holds without
*q* and vice versa, showing a failure of sufficiency exactly
because more worlds are considered.



The key to solving the paradoxes and approaching universality, on this
approach, is to broaden the collection of worlds, in order to sieve
out what sufficiency relations persist. Sylvan extends this strategy
to deal with other paradoxes of implication, such as the irrelevant \(
q \rightarrow (p \rightarrow p) \).



Since \(p\) *does* imply \(p\), \(p \rightarrow p\), i.e., at
every world in which \(p\), also \(p\), then to show that arbitrary
\(q\) is not sufficient for this self-implication, there needs to be a
counterexample: one where \(q\) holds without \(p \rightarrow p\).
Generally, to preserve sufficiency, the same strategy goes for any
logical truth, \(B\): if we are to avoid \(A \rightarrow B\) when
\(B\) is logically necessary but irrelevant to \(A\), there must be
points at which *even logical truths fail*. For example, there
would be a world at which the law of non-contradiction \(\twiddle (A
\amp \twiddle A)\) fails. These points are known as non-normal or
impossible worlds, about which there is a growing literature (e.g.,
Nolan 2013; Berto and Jago 2019).



The logics being proposed here, then, are naturally
*paraconsistent*: they do not validate the "spread"
law: (\(p \amp \twiddle p) \rightarrow q\), and so can putatively
handle inconsistency without collapse into triviality. (In
*Sociative Logics*, Sylvan refers to these as
*pararelevant* logics.) Indeed, with counterexamples to the law
of non-contradiction, there would be worlds where some sentences are
*both true and false*.



The first relevant logics were presented proof theoretically, in terms
of axioms and closure under rules. The need for a model theoretic
interpretation (given in a classical metatheory) resulted in
Sylvan's co-development with Plumwood of ternary relation
semantics for first degree entailment relevant logics (Routley and
Routley 1972) and the ensuing Routley-Meyer partnership that proved
and extended a range of results for relevant logics (cf. Routley,
Meyer, *et al.* 1982; and Brady 2003). (Cf. Fine 1974; Urquhart
1972.) A *Routley-Meyer frame* \(\langle W, N, 0, R, {}^\*
\rangle\) consists of:


* a set of worlds \(W\),
* among which are the normal worlds \(N\), the others being
non-normal;
* a distinguished world \(0\), thought of as our actual world;
* a three-place relation between worlds \(R\);
* and a function \(^\*\) from worlds to worlds called the *Routley
Star*.



An evaluation then assigns formulas a truth-value at each world; so
some \(p\) may be true at one world but false at another. With the
Routley star, these may even be the same world. The conditions on
implication and negation are as follows:


* \(A \rightarrow B\) is true at world \(x\) iff for all \(y, z\)
such that \(R(xyz)\): if \(A\) is true at \(y\), then \(B\) is true at
\(z\)
* \(\twiddle A\) is true at world \(x\) iff \(A\) is false at world
\(x^{\*}\).



Nothing prevents both \(A\) and \(\twiddle A\) being true at some
worlds; indeed, respecting relevance demands it. These conditions can
be seen as *generalizations* of more standard ones: in the case
of implication, if \(y = z\) then this is just a modalized material
conditional in a Kripke frame; in the case of negation, if \(x = x^\*\)
then this is just the clause for negation in classical logic. For
further details, see the entry on 
 relevance logic, 
 Mares (2004), and Priest (2008, ch. 10). On the Routley star see
Restall (1999).



Routley/Myer semantics has generated an enormous secondary literature
(cf. the secondary literature section of the bibliography), for
example Copeland 1979, 1983, Thomas 2015. Debates have surrounded: the
interpretation of the semantics (e.g., the ternary relation, the
Routley-star operator, non-normal worlds); alternative semantics for
relevant logics; the adequacy of non-classical responses to semantic
and set-theoretic paradoxes; dialetheism; and naive set theory.
For recent work about the ternary relation see Beall et al 2012; for a
recent exchange about the Routley star and negation, see Berto 2015,
De and Omori 2018, and Berto and Restall 2019.


#### 2.2.3 Inconsistency



Sylvan's instrumental need for inconsistent worlds in order to
account for implication led to tentative endorsement of the
possibility of true contradictions (dialetheism). Most relevant
logicians thought of these "worlds" merely as artefacts of
the semantics, not as legitimate possibilities
(indeed--they're impossible!); but there the idea was, of
"dialectical" or contradictory worlds. By (1976), he and
Meyer consider a rather literal interpretation of Hegelian dialectic,
and openly question the "Consistency Hypothesis" that the
world is consistent. They urge instead a "dialectical"
possibility. They present the (relevant) logic *DL* (for
dialectical logic), and give it an axiomatization that explicitly
includes an outright contradiction \(p \amp \twiddle p\) as an
*axiom*. (Smiley calls this "Routley and Meyer's
war work" (Smiley and Priest 1993, 17). See also van Benthem
1979, Havas 1981, Ficara 2021.)



When Graham Priest arrived in Australia and presented his 'Logic
of Paradox' to the 1976 meeting of the Australasian Association
of Logic, another intensely productive partnership was struck. With
true contradictions--later to be named *dialetheia* by
Sylvan and Priest--in view, the potential of surpassing classical
logic opened up:



> 
> 
> The liberating effect of giving up the classical faith ... is
> immense: ... one is free to return to something like the grand
> simplicity of naive set theory, to semantically closed natural
> languages (having abandoned the towering but ill-constructed and
> mostly unfinished hierarchies of formal languages), and to intuitive
> accounts of truth, of proof, and of many other intensional notions
> (1979b, 302).
> 
> 
> 



Dialetheism, especially due to Priest, has prompted a long and growing
discussion (see Priest 1987 [2006] and Beall 2009 for defences and
e.g., Field 2008 for some useful criticism; see the bibliography in
the entry on 
 dialetheism for more).



Sylvan's thinking about contradictions evolved, depending on his
co-author, even over the course of a book. In *Relevant Logics and
their Rivals* (1982), early chapters float dialetheism as a
hypothesis, in an "agnostic" spirit (61), or that of
taking precautions; whereas later in the book, it states bluntly that
"mathematics is inconsistent" (255). (The shift is
criticized by Urquhart in a 1988 review (Brady 2003, 2).)



As mentioned in the quote above, Sylvan saw that something like the
"dialectical logic" *DL* could be used to
underwrite inconsistent but non-trivial mathematical and scientific
theories, which had been of interest to him since the start. Of
particular note is naive set theory, used by Cantor, Dedekind,
and Frege in the foundations of mathematics (see the entry on 
 the early development of set theory), 
 but dealt an apparently fatal blow by Russell's paradox circa
1900. Building from work by Brady (1971), naive set theory as
formulated with the implication connective
'\(\rightarrow\)' of *DL* (or the slightly
weaker *DK*) takes as axioms that there is a set for every
property \(A\), i.e.,

 

\[ 
\mathrm{P}y \mathrm{U}x (x \in y \leftrightarrow A(x)) 
\]


where '\(\in\)' is read 'is a member of' and
with Sylvan's preferred particular and universal quantifiers
(see Section 2.1); and that sets are determined by their members,
i.e.,

 
\[ \mathrm{U} z (z \in x \leftrightarrow z \in y) \rightarrow x = y. \]


On the basis of these axioms, *comprehension* and
*extensionality*, in Routley (1977) he begins to sketch out
what he hopes will be the "rehabilitation" of naive
set theory and more using ultralogic.



A basic derivation in this set theory is that the Russell set exists,
and is both a member of itself and not a member of itself. The
paradoxes, in other words, are *proofs*, and the resulting
contradictions are *theorems* (1979b, 302). Sylvan sketches the
further work needed to show that elementary principles such as the
Zermelo-Fraenkel axioms and their immediate consequences can be
derived. And he speculates, much more ambitiously, that the Axiom of
Choice and the Continuum Hypothesis could be decided as well; see
Weber (2012). Priest 2006, chapter 18 is a discussion of
*paraconsistent set theory* in this tradition.



The project was given an essential boost when Brady confirmed the
non-triviality of the theory in the late 70s, i.e., that there are
(absurd) sentences that *cannot* be proved in this theory,
results which appeared as Brady (1989); see (Brady 2006). Further work
in relevant arithmetic, by Routley, Meyer, Mortensen, Dunn, Priest,
Restall, and others, followed. This led to the area now known as
*inconsistent mathematics*, carried forward especially by
Mortensen (1995, 2010), where e.g., the Routley star is used as a
*functor* to great effect; see the entry on 
 inconsistent mathematics 
 for further references, and Weber 2022.



Sylvan saw relevant logics as only one type of what he termed
*sociative logics*, logics that require some meaningful
association or connection between premises and conclusions of valid
arguments, or antecedents and consequents of valid implications. Along
these lines, he contributed to the development of *connexive*
logics, systems that include principles like so-called
Aristotle's thesis, \(\twiddle (A \rightarrow \twiddle A)\).
Standard relevant logics and non-classical logics more generally
usually only deny some classically valid principle. Connexive logics
are in some ways even more radical than relevant logics, because they
are *contra-classical*--e.g. since Aristotle's
thesis is invalid according to classical logic. See the entry on
 connexive logic 
 and Sylvan 2000a.


### 2.3 Applications



This section mentions briefly some other applications of
Sylvan's preferred logics to a wide range of philosophical
problems. Sylvan saw applications as a test for the choice of such
theories over rival logics. Sections 3 and 4 are in a way extended
discussions of such applications. Sylvan argued that relevant and,
more broadly, what he termed "sociative logics" had
applications in areas as diverse as causation, an analysis of
knowledge, vagueness (including the idea that there are vague objects;
see Sylvan and Hyde 1993), and value theory. Here we sketch two such
applications, in confirmation, and computation.


#### 2.3.1 Confirmation



Following Goddard (1977), Sylvan (along with Nola, in 1991) applies
relevant logic to solve the *paradoxes of confirmation* made
famous by Hempel. These are problems in philosophy of science about
formulating inductive generalizations such as


1. All ravens are black,



which is confirmed by instances of things which are both black and
ravens; but the universal generalization is logically equivalent to
its contrapositive form


2. All non-black things are non-ravens,



which would similarly be confirmed by any non-black non-raven; but
since e.g., a red pencil is obviously *not* confirmation that
all ravens are black, something has gone wrong. For Sylvan, the
problem--as is often his diagnosis--lies in the
formalization of the natural language claims--"It is
well-known in relevance circles that the most outrageous of these
paradoxes are automatically removed by replacement of the material
conditional ..." (2000a, 227). "A relevance
shift," he argues with typical restraint, "is a sure-fire
way of knocking out all the paradoxes of confirmation" (2000a,
232.). For discussion, see Fitelson (2006).


#### 2.3.2 Computation



Along other lines, Sylvan made tentative steps in the foundations of
recursion theory, towards a non-classical theory of computation (cf.
Copeland and Sylvan 1999; Sylvan 2000a). According to work by Turing,
Church, and Godel in the 1930s, computers face logical limits on
what they can compute (see the entry on 
 The Church-Turing Thesis 
 and the entry on 
 computability and complexity). 
 Uncomputability proofs, though, bear a very strong resemblance to the
derivations of Russell's paradox and other diagonal
paradoxes. If "dialectical" logic can be used to solve
those paradoxes, though--essentially, by accepting that they have
truly contradictory conclusions (see Section 2.2 above)--then
could the same be done in the case of computers? Then the conclusion
would be, *not* that there are uncomputable algorithms, but
rather "there are more algorithmic functions than all
algorithmic functions" (2000a, 195). Sylvan envisions
"dialeth[e]ic machines"; cf. Weber (2016).


### 2.4 Summary



Sylvan's approach to logic is of a piece with his work in
metaphysics and ethics: a polemical rebuke of the perceived powers of
the day--in the case of logic, the hegemony of classical
logic--and a highly imaginative and open-minded attitude towards
what sorts of entities--possible and impossible alike--our
best theories should condone. We turn now to these other aspects of
his work.


## 3. Ontology and Metaphysics



In this section, we present Sylvan's work in ontology and
metaphysics. As discussed below, Sylvan was deeply inspired by Alexius
Meinong but, as a matter of terminology, their understanding of
'ontology' and 'metaphysics' differ: while
Meinong would situate metaphysics and ontology as small corners within
a more general object theory, Sylvan situated them the other way
around. (See, for instance, Meinong 1904, SS2 and SS11; Sylvan
1995a, 47). In what follows, we follow Sylvan and employ what we take
to be contemporary standard usage of 'ontology' (roughly
understood as the study of what exists and what does not) and
'metaphysics' (roughly understood as the study of the
structure of reality), while acknowledging that Meinong-scholars might
dispute this use of terms. In Section 3.1, we sketch some of the
essential features of *noneism*, that is, Sylvan's theory
about non-existent objects. In Section 3.2, we discuss Sylvan's
attempt at expanding the horizons of traditional ontology by
developing a new theory called *sistology*. Finally, in Section
3.3, we summarize Sylvan's heterodox account of pluralism,
labelled *plurallism*.


### 3.1 Noneism



From 1965 on, Sylvan argued that, through the influence of Quine,
contemporary philosophy is committed to a fundamental mistake. Such a
mistake, labelled the "Ontological Assumption" (cf. 1980),
is represented by the view that one cannot make true statements about
what does not exist. In opposition to this idea, Sylvan develops a
theory about (non-existent) objects or, in Sylvan's jargon,
items--*noneism*.



> 
> 
> [Noneism is] a very general theory of all items whatsoever, of those
> that are intensional and those that are not, of those that exist and
> those that do not (...); it is a theory of the logic and
> properties and kinds of properties of all items (1980, 5-6)
> 
> 
> 



Sylvan's intuition is that, in order to be able to say something
true about non-existent items, we need to allow for the possibility
that non-existent items have properties. For instance, in order to be
able to say that 'Sherlock Holmes is a detective' is true,
Sherlock Holmes needs to have the property of *being a
detective*. Now, according to Sylvan, a suitable philosophical
background for supporting this intuition is Meinong's *Theory
of Objects*. For this reason, in *Exploring Meinong's
Jungle and Beyond* (Routley 1980), Sylvan tries to deliver a
modern logical presentation of Meinong's philosophy. He
writes:



> 
> 
> Meinong's theory provides a coherent scheme for talking and
> reasoning about all items, not just those which exist, without the
> necessity for distorting or unworkable reductions; and in doing so it
> attributes ... features [properties] to nonentities [non-existent
> objects] (1980, iv-v).
> 
> 
> 



At nearly 1000 pages, Routley (1980) develops noneism in great detail.
We summarize it in five main theses, which represent the core
assumptions of what Sylvan calls *minimal noneism* (from now on
**MN**). First of all, following Meinong's account
of intentionality, Sylvan believes that:



**(MN1)**
"everything whatever (...) is an object [an
item]"


(1980, 1-2; 352). In other words, every time we refer to
something, we refer to an item. If I tell a story about Sherlock
Holmes, I tell a story about an item, namely that item that is the
subject matter of my story.



The second thesis is that:



**(MN2)**
"very many objects [items] do not exist"


(1980, 2-3). Sylvan follows Meinong in claiming that some items
exist (e.g., the Eiffel Tower) and some others do not (e.g., Sherlock
Holmes). Like Meinong, Sylvan treats existence as a property: some
items have the property of *being red* and some other items do
not; some items have the property of *being existent* (e.g.,
the Eiffel Tower) and some items do not (e.g., Sherlock Holmes). When
items do not have the property of *being existent*, they are
non-existent items. In Sylvan's jargon, they are
"nonentities".



Furthermore, according to the third and fourth theses:



**(MN3)**
"non-existent objects [items] are constituted in one way or
another"


(1980, 2-3), and



**(MN4)**
"every object [item] has the 'characteristics'
it has irrespective of whether it exists"


(1980, 2-3). Thesis **(MN3)**
corresponds to Meinong's *indifference principle*: the
properties an item has are indifferent to the ontological status of
the item itself. Thesis **(MN4)** corresponds
to Meinong's *independence principle*: an item's
*having properties* is independent of whether the item in
question exists or not.



As many have pointed out (cf. Russell 1905 and 1907; see also Berto
2013 and Priest 2005), the original theory defended by Meinong faces
problems. In particular, Meinong's theory is threatened by
*triviality* (Berto 2013, 106-107); that is, the
situation in which everything exists--including items that
clearly do not. E.g., if I refer to not just to Sherlock Holmes but to
"the *existing* Sherlock Holmes", then it seems by
**(MN4)** that Sherlock Holmes exists.



In order to resolve this issue, Sylvan makes two moves. First of all,
he introduces the distinction between characterizing and
non-characterizing properties. The former are necessary in order to
define the essence of an object. A characterizing property is a
property (e.g., *being a detective* or *being smart*)
that is necessary in order to make a specific item (e.g., Sherlock
Holmes) the item that it is. Using Sylvan's words:



> 
> 
> Characterizing predicates [or properties] are those which specify what
> an item is like, in itself. They tell how an item is in fact. They
> give its description. A good dossier of an item would perhaps give its
> characterization first, by way of its characterization features [or
> properties] (Sylvan 1995b).
> 
> 
> 



On the other hand, the non-characterizing properties are all those
properties that are not characterizing. According to Sylvan, the
property of *being existent* is a non-characterizing
property.



As it has been extensively argued in the secondary literature (see,
for instance, Priest 2005), the difference between these two kinds of
properties is unclear. It is also fair to say that, even though some
(neo-)Meinongians have tried to cash out such a distinction in more
precise terms (see, for instance, Jacquette 2015 and 2017; Parsons
1978 and 1980), there is little consensus that any progress has been
made. That being said, even though it is certainly difficult to have
strict criteria to separate the characterizing properties from the
non-characterizing ones, it is absolutely clear that:



**(MN5)**
"neither existence nor non-existence is a characterizing
property"


(1980, 2). This is the fifth and last thesis.



The second move Sylvan makes in response to the triviality problem is
represented by the idea that, even though it is the case that every
time we refer to something we refer to an item, the item in question
has characterizing properties. Following Berto (2013), we can also say
that, consistent with some other neo-Meinongians (i.e., Jacquette
2015; Parsons 1980), Sylvan argues in favour of the following
*characterization principle*:



> 
> 
> for any set of *characterizing* properties, some item satisfies
> it.
> 
> 
> 



Consider, for example, Sherlock Holmes. When we refer to Sherlock
Holmes, we refer to an item (because of
**(MN1)**). Moreover, even though Sherlock
Holmes does not exist (because of **(MN2)**),
he has some characterizing properties (because of
**(MN3)** and
**(MN4)**). For instance, according to
Doyle's novels, Sherlock Holmes is a smart detective. If so, in
Sherlock Holmes's set of characterizing properties, there are,
at least, two properties: *being a detective* and *being
smart*. However, the property *being non-existent* is not
in this set because it is a non-characterizing property. And this is
guaranteed by **(MN5)**.



As we have already specified above, *minimal noneism* is merely
the core of Sylvan's noneism which is more elaborate and
sophisticated than sketched here. Exactly because of its complexity,
noneism forces us to rethink some of our traditional approaches to
important philosophical topics. Examples are intensionality,
nonexistence, impossibilia, and paradoxicality. Moreover, in the light
of these conceptual innovations, Sylvan also discusses some of the
relevant applications of noneism in philosophy of mathematics (cf.
1980, 769-781 and 791-833), philosophy of perception (cf.
1980, 649-678), philosophy of time (cf. 1980, 361-410);
philosophy of science (cf. 1980, 781-791) and philosophy of
fiction (cf. 1980, 537-595).



Sylvan spent many years developing and defending noneism, but he was
not entirely satisfied with it. He had two major complaints. On the
one hand, he thought that his way of presenting noneism was
rhetorically problematic: EMJB was too long, rambling, and not
incisive enough. As such, EMJB needed to be rewritten (see Sylvan
1995b). On the other hand, he aimed at "liberalizing
noneism" by allowing all items to have both characterizing and
non-characterizing properties (Sylvan 1995b). Archival documents show
that, to this end, Sylvan tried to develop a new theory that has many
features in common with so-called "modal Meinongianism",
recently defended by Priest. On these issues, see Casati (2018),
Griffin (2018), Kroon (2019), Priest (2005).


### 3.2 Sistology



In late life, Sylvan aimed at enriching the ideas defended in Routley
(1980) by developing what he calls "sistology". On the one
hand, sistology adopts all the fundamental ideas of noneism. Like
noneism, sistology includes items that do not exist (cf. Sylvan 1991,
837; 1997, 11-12) and it accepts that those items have
properties (cf. 1991, 838-39). On the other hand, sistology
develops and enriches noneism in the following ways.



To begin with, Sylvan tried to move the focus of his attention from
the existence (or non-existence) of items to their *being
items*. Using Sylvan's words, sistology is concerned with
"all items as *having standing*" (1991, 838). Thus,
sistology aims at casting a new light on what it means to *be an
item* instead of showing that it is possible to have non-existent
items. The latter project was the unique task of noneism.



Secondly, Sylvan tried to extend and deepen the catalogue of items he
dealt with in Routley (1980). In an unpublished manuscript, Sylvan
described an imaginary museum in which all sorts of items are
accepted. Among those items that have not been (comprehensively)
discussed in his (1980), Sylvan listed:


1. *vacancies*, *vacuums* (such as holes, empty bowls,
valleys, and absences);
2. *wholes, aggregations* (such as the totality, everything,
the universal set, and the Cosmos);
3. *significant ideological objects* (such as the Tao,
Buddhist ultimate reality, Nirvana, Jehovah); and
4. *inconsistent objects* (such as the square circle).



In particular, Sylvan devoted significant effort to this last cluster
of items, underscoring the idea they require the employment of a
paraconsistent logic. Given that inconsistent items have inconsistent
properties, if classical logic is employed then triviality immediately
follows. In order to avoid trivialism, the adoption of a
paraconsistent logic is required.



> 
> 
> Consider, for instance, inconsistent objects. (...) By virtue of
> what they are, they have contradictory properties, thereby
> trivializing any theory built upon mainstream logic. An authentic
> sistology requires logical reformulation of a more demanding
> paraconsistent type (Sylvan 1991, 839).
> 
> 
> 



The third and last attempt to develop noneism is represented by a
serious engagement with the notion of a "source". As he
had already discussed, a "source" is what allows us to
understand the charactering properties that an item (cf. 1980, 463;
1995a). The source of Anna Karenina's characterizing properties
is Tolstoy's *Anna Karenina*. In sistology, Sylvan aims
at deepening our understanding of sources by admitting that not all of
them are equally reliable. For instance, optical illusions teach us
that visual perceptions are not always a trustworthy source for
characterizing the items we see. For this reason, Sylvan suggests
introducing two kinds of predicates. The first kind (call them
"*ordinary* predicates") tell us how items look;
the second kind (call them "*non-ordinary*
predicates") tell us how items really are.



> 
> 
> Not all sources are always reliable or otherwise satisfactory; for
> example, perceptual sources are notoriously unreliable as to how
> things *really* are. (...) Thus, [the] division of
> [ordinary and non-ordinary] properties is presumed (1991, 839; italics
> ours).
> 
> 
> 



Sistology, which is only sketched by Sylvan, nevertheless anticipates
some of the ideas currently debated among neo-Meinongians, for
example, as discussed above, with "items in general".
Regardless of the existence or non-existence of these items, sistology
concerns their "having standing" (1991, 839). In so doing,
Sylvan focuses his attention on one of the most under-researched
notions of Meinong's theory of objects, that is, the so-called
doctrine of *Outsidebeing* [*Aussersein*]. Only recently
have neo-Meinongian started to turn their attention to this topic
(Casati and Priest 2017; Grossman 1974; Jacquette 2015). So too with
the very particular kind of object that is "nothingness"
(cf. Sylvan 1995a). After a long-standing lack of interest in these
topics, neo-Meinongians have begun to take them into serious
consideration as well (Casati and Fujikawa 2019; Priest 2014a and
2014b; Jacquette 2013).


### 3.3 Plural(l)ism



In the current philosophical landscape, there are many different forms
of pluralism on offer. For instance, there is an *ontological*
form of pluralism (there are different ways of being), *truth*
pluralism (there are different ways of being true), and there is a
*logical* form of pluralism (there is more than one correct
logic; see the entry on 
 logical pluralism). 
 However, it is almost universally assumed, if mostly unstated, that
there can be no pluralism about the *actual world*--this
one is the only *actual* one. As should appear clear from this
entry, though, Sylvan was accustomed to challenging the philosophical
consensus. He began by attacking classical logic, he continued by
questioning the so-called Ontological Assumption and, late in his
career, he decided to challenge what he calls *one-world-ism*,
that is, the idea that there is only one actual world. (For another
example of a philosophical position which considers a plurality of
actual worlds, see Goodman (1978).)



Sylvan argues that there is a plurality of actual worlds we all live
in. In his *Transcendental Metaphysics* (1997) he claims:



> 
> 
> A theme, to be defended at length, is that while there is *an*
> actual world, which is suitably external, mind-independent,
> perceiver-independent, and the like, it is not unique. *There are
> many actual worlds*. That theme is bound to strike others, as it
> still occasionally strikes me momentarily, as utterly outrageous. [My]
> work and arguments are designed to remove this misconception (1997,
> 4).
> 
> 
> 



In order to draw a clear distinction between his pluralism and the
others, he refers to his own theory with a neologism:
*plurallism*. The aims of such a theory are summarized as
follows:



> 
> 
> The overarching themes of plurallism are (...): (1) *There is
> no unique world. There is no unique actual universe*; (2)
> *There is no one unalterable truth; no single Way of Truth*;
> (3) *There is no single correct Scientific Theory* (1997,
> 4).
> 
> 
> 



In order to support these ideas, Sylvan presents two sets of
arguments.



Sylvan argues *indirectly* there is a lack of (good) arguments
in favour of the uniqueness of the actual world. From the fact that
there is such a thing as an actual world it does not necessarily
follow that such a world is unique, nor is its uniqueness observable
(cf. 1997, 54-60).



On the other hand, he *directly* supports plurallism by arguing
that for each area of research, there is (or there could be) a
plurality of correct theories. His reasoning goes as follows. All
theories are grounded on logic because logic is necessary for
reasoning about both the data used by those theories and the theories
themselves. And, if there is, not just one, but a *plurality of
correct logics*, there is (or there could be) a plurality of
correct theories which spring from all those different, but all
equally acceptable, ways of reasoning as well (cf. 1997, 61-74).
From this, a plurality of actual worlds follows if we accept two
enthymematic assumptions. The first one is that any correct logic, in
virtue of its being correct, properly describes an actual world. If
so, if there is more than one correct logic, there is more than one
actual world too. The second assumption, then, is that there are many
correct logics. This idea was not shared by Sylvan's
contemporaries but one that he came to defend late in his career,
claiming (1997, xix) "that not merely is there a plurality of
logics, but there is also [a plurality] of correct logics". The
idea is elaborated on in Sylvan (1997, ch. 4) and is now widely
discussed in the literature (see, for instance, Beall and Restall
2000; Russell 2008; Weber 2017b). Sylvan claims that phenomenological
data seems to support plurallism as well (cf. 1997,
118-133).



Sylvan's motivations for developing plurallism are not uniquely
philosophical. On the contrary, he believes that the existence of the
plurality of actual worlds can have important political consequences
too. One of those consequences is the extension and strengthening of
our idea of tolerance. According to Sylvan, intolerant behaviours are
often, if not always, grounded on ideologies driven by what he calls
the "*one-true-way*" (1997, 462) or the
"*one-admissible-way*" (1997, 462). Governments,
religious groups, and even scientists believe that "truth should
be imposed" (1997, 462) where truth is what is *uniquely*
determined by them. Plurallism invites us to entertain the idea that,
as there is no such thing as a unique actual world, there is no such
thing as a unique truth. And this should undermine the ideological
roots of intolerant behaviours.


### 3.4 Summary



In many ways, Sylvan's philosophical and logical research is
devoted to the attempt to be inclusive, open-minded, and, therefore,
tolerant. *Contra* the Quinean admiration for desert landscape,
Sylvan admired an over-crowded jungle of ideas in which different
logics, all sorts of items, and a plurality of actual worlds could
peacefully coincide.


## 4. Moral Philosophy



In this section we describe Sylvan's work in moral philosophy.
His seminal and frequently reprinted (1973; see also the entry on
 environmental ethics 
 Section 2) was, alongside Naess (1973), the first published work in
environmental ethics and began a central debate in the area, one
concerned with intrinsic value in nature. Elaborated on in Routley and
Routley (1979b) and (1980a), this work developed arguments against
what he termed "human chauvinism"--the view that
humans are exceptional in being the sole locus of intrinsic value, all
else having merely instrumental value. Alongside this work in
environmental ethics more broadly, which was to continue until his
death, he also published in defence of pacifism, against nuclear war,
and was one of the first philosophers to point to the emerging moral
issues associated with anthropogenic global warming.


### 4.1 The Last Man Example



Developing out of influential work condemning Australian forestry
practices in the early 1970s, (cf. Routley and Routley 1973a, Byron
1999), Routley (1973)--"Is There a Need for a New, an
Environmental, Ethic?"--presents a thought experiment
designed to test what Sylvan took to be a core principle of Western
ethical systems, the Freedom Principle:



> 
> 
> One should be able to do what he wishes, providing (1) that he does
> not harm others and (2) that he is not likely to harm himself
> irreparably (1973, 15)
> 
> 
> 



He calls this principle *basic human chauvinism* "because
under it humans, or people [whether present or future], come first and
everything else a bad last"--a view later characterized as
"anthropocentric" in the much expanded discussion of The
Last Man Example in Routley and Routley (1980a, cf. 96).



We are invited to consider a world in collapse where humanity is
reduced to a single person who then proceeds to eliminate, to the best
of their abilities, "every living thing, animal or plant (but
painlessly if you like, as at the best abattoirs)." (1973, 16)
With the demise of the last man (which we may suppose occurs
immediately prior to the wholesale destruction unleashed), there are
no humans--either others or the last man himself--who could
be harmed by such an act and so, with clauses (1) and (2) satisfied,
the act is permissible according to the "human chauvinist"
Western ethical systems. (And even if "others" were
extended to include non-human sentient creatures, still no harm,
understood as suffering, would accrue given the act is done
"painlessly".) Yet, "what he does is wrong"
and therewith we have a counterexample to such chauvinism and
associated Western ethical systems, and a claimed need for a new
ethic, "an environmental ethic", capable of accounting for
the wrongness of the last man's act. (As in his logical work,
Sylvan's strategy is to try to isolate what is sufficient (in
this case, for wrongness) by considering "distant"
possible worlds.)



Granting the wrongness of the last man's act, is a "new
ethic" really required? Preference utilitarianism has been
considered as a "traditional" ethic capable of condemning
the last man. (Cf. Elliot 1980, 20 and 23; and Carter 2004,
51-52 for a more limited condemnation along preference
utilitarian grounds.) Where there is an overwhelming preference for
preservation of the world beyond the death of the last man, and its
destruction would thus harm those having such a preference, the
Freedom Principle would already appear to prohibit such an act
(assuming the aggregated harm outweighs any benefit in the
satisfaction of contrary preferences). But notice that condemnation,
on this view, is highly contingent, depending on people's
preferences (condemnation is justified *only if* preferences
conflict with destruction). Since the condemnation is thought to be
warranted with "no ifs and buts", yet this
"traditional" response offers the correct judgement only
in special circumstances, for Sylvan, it counts as "too
parochial" (Routley 1973, 20). (Cf. Lamb 2018, 532-3 for a
similar point.)



Reacting, in part, to Leopold's call for a "land
ethic", Sylvan's subsequent work in the area (much of the
early work with Val Routley, later Val Plumwood) proceeds to describe
and argue for just such a non-anthropocentric, environmental ethic. A
dominant aspect of this "new" ethic (indeed, a
*characterising* feature in Elliot 1980) that was fixed on by
subsequent authors was the extension of non-instrumental,
"intrinsic" or "final" values to the non-human
world. First mentioned in 1974 in early drafts of Routley and Routley
(1980a) and subsequently Val Routley (1975), Rolston (1975), and
Callicott (1979)--who all employ versions of the Last Man
Example--the extension is described and defended at length in
Routley and Routley (1980a). (Sylvan assumes intrinsic value is, in
general, already assured on the familiar Aristotelian ground that
instrumental value requires intrinsic value, lest vicious regress
ensue--cf. Aristotle *Metaphysics*, 994b9-15.)



Sylvan and Plumwood hypothesise that what underpins the deontic
prohibition of the last man's act is the truth of the
axiological claim that entities in non-human nature can possess more
than mere instrumental value--non-human nature "can have
value and create obligations not reducible (in any way) to human
interests" (1980a, 129). While such items may have instrumental
value, value as a means to human ends, advantaging us in various
ways--e.g., the value of forests in supplying water for human
consumption--they might also have "non-instrumental",
or what the Routleys called "intrinsic" value (1980a, 126
and 129). Thus, the rejection of human chauvinism in its deontological
form (the assertion of and the argument to the falsity of the Freedom
Principle) was accompanied by its rejection in axiological form: not
only humans have intrinsic value; non-human nature may also be the
locus of intrinsic (non-instrumental) value.



While accepting that we may have moral obligations with respect to or
regarding entities in the non-human world, Routley (1973, 19) and
Routley and Routley (1980a, 174ff) deny that this entails our having
obligations *to* them and deny, too, their having correlative
rights. Sylvan rejects such an extension of rights to non-human
entities. For this reason, he takes the "new environmental
ethic" to "differ markedly" from alternatives like
Leopold's land ethic. As it developed, it also differed markedly
from most forms of utilitarianism for a broad range of reasons,
arguing instead for a deontologically constrained "optimisation
approach to value theory". (See Routley and Routley 1985; Sylvan
1992.) Variants of Last Man counterexamples to traditional Western
ethics are also taken to show that the distribution of intrinsic value
extends beyond sentient individuals--contra "animal
liberationists" (1980a, 125) like Singer--so that
"candidates for value ... include all objects"
(1980a, 140).



Resisting Sylvan's broad push for a non-anthropocentric,
environmental ethic are several arguments suggesting the inevitability
of human chauvinism. Foremost among them are arguments that, he
claims, "parallel" arguments for egoism. Their rejection
follows similar grounds for rejection of egoism--cf. Routley and
Routley (1979b, esp. 47). This paper also distinguishes strong forms
of human chauvinism (endorsing what Sylvan later termed the sole value
assumption: that *only* members of the human class and some of
their possible states have intrinsic value) from weaker forms that
merely endorse, for example, "the Greater Value Thesis: the
invariable allocation of greater value or preference ... to
humans, while not however entirely excluding non-humans from moral
consideration" (*ibid*., 36)--a thesis also rejected
by Sylvan. Paske (1991) defends a qualified version of the thesis; the
moral differentiation in favour of *most* humans can be
justified (by appeal to deontologically-constrained hedonic
consequentialism). Attfield (1981), considering versions of the Last
Man Example, also rejects strong human chauvinism while defending the
greater value thesis, thus defending a weak chauvinism in
Sylvan's sense. "The good of trees might outweigh some of
our whims: but it does not outweigh our interests except where our
interests depend on it" (1981, 51).



Petersen and Sandin, on the other hand, defend a strong form of human
chauvinism, arguing that the Last Man Example is subject to varying
responses depending on the *motives* attending the act of
elimination. They thus reject the hypothesis of intrinsic values in
nature, arguing instead that any supposed wrongness "can be
better explained by precepts about last man's character traits
and motives" (2013, 133). It remains open whether such a
response is adequate for the Last People Example (described by Sylvan
immediately following the Last Man Example) who may be said to act
"for the best of reasons" though they have acted
"badly" (Routley 1973, 16-17).



A number of arguments against Sylvan's hypothesised intrinsic
value of natural items focus on supposed problems that attend the
apparently "cosmic" account of value that items are said
to have in the absence of valuers (e.g., after the demise of the last
man). Some focus on problems traditionally associated with moral
objectivism. If value is conceptually independent of valuers then:
moral intuitionism is an unacceptable consequence (cf. Mannison 1980,
57, the charge of "realism"); moral theory is inconsistent
with (the preferred theory) moral projectivism (Carter 2004, who
claims a projectivist theory can explain our intuitions concerning the
last man); or such value is simply beyond epistemic access and
irrelevant for decision-making (Justus *et al.* 2009,
187-8). The latter point echoes earlier claims in Thompson
(1990), Grey (1993), and Fox (1995) that the hypothesis of intrinsic
value in nature results in values that, being too far removed from
human concerns, are irrelevant as an ethical guide to human action
(Thompson 1990, 159-60; Grey 1993, 464) and, in any event, are
unnecessary--an enlightened anthropocentrism is sufficient.



Sylvan's position on the ontology of values (discussed at length
in 1980a, esp. 152ff) draws on the Last Man Example to claim that
things can, indeed, be valuable at a time when no valuers exist and
extended thought experiments of a similar kind he takes to further
establish that things can be valuable in a world wherein no valuer
exists at all, though a valuer must exist in some world (1980a, 156,
fn 67; cf. also Sylvan and Bennett 1994, 143). Values are, he claims,
conceptually dependent on valuers--thus the slogan "no
value without valuers" remains true, he contends--and
therewith the rock of objectivism is said to be avoided (1980a, 154).
Elliot (1980) also contends that a non-objectivist account is
sufficient for this kind of value engendered by the last man example,
though it is one requiring *actual* evaluators ("no
values without actual valuers"). He goes on to describe a
*subjectivist* account that further links values to valuers in
a manner that "makes the valuer the sole determinant of a
thing's value" (1980, 19) with value reduced to valuer
evaluations.



Taking himself to have avoided objectivism, Sylvan nonetheless argues
against subjectivist accounts--intrinsic values are not
subjective either (1980a, 154). Intrinsic value *in a world*,
while depending conceptually on valuers, nonetheless does not reduce
to valuers *in that world* in any way. Some have remarked on
the apparent similarities between Sylvan's account of intrinsic
value and secondary qualities, suggesting his account amounted to a
response-dependent account of intrinsic value (cf. Grey 2000). See
Lamb (2018, SSIX) for argument to the contrary.



In the further elaboration of the "new ethic", Routley and
Routley (1980a) develops a multiple factor model combining traditional
values, such as the virtues and creature enjoyment, with environmental
value-making factors, for example: diversity of systems and creatures,
naturalness, integrity of systems, stability of systems, and harmony
of systems (170-171). So the shift to an environmental ethic
does not reject ordinarily acknowledged welfare values for persons or
humans, but simply recognises a further set of factors contributing to
intrinsic value in nature (171). Such value-making factors enter into
a mutually constrained optimisation so that the increase of one need
not increase the overall intrinsic value of the entity exemplifying
it; thus, an increase in diversity in a forest may decrease value
insofar as it may come at the cost of naturalness (e.g., if the added
diversity comes from the anthropogenic addition of feral species not
naturally occurring in that forest).



The account of value is non-naturalistic in the sense that value is
argued to be irreducible to natural features, even though
"grounded" in them. (1980a, SS5; Sylvan later
committed to the supervenience of intrinsic value on naturalistic
features, Sylvan and Bennett 1994, 143). It is Meinongian in a number
of respects--most obviously, drawing freely on Routley (1980),
cf. esp. SS8.11, values are features had by items but, like
properties, they do not exist (1980a, 153ff). Sylvan's moral
epistemology also draws heavily on Meinong's account of
"emotional presentation" (see Lamb 2018, SSVIII):
"the valued object may be emotionally presented and its value
*thus* recognised, without its value simply amounting to its
emotional presentation" (Routley and Routley 1983, 453). The
account is articulated at length in Sylvan (1986). Perhaps
unsurprisingly, Sylvan's semantic analysis of value (cf. Routley
and Routley 1983) makes use of non-classical, relevant logic in its
formal analysis. (Weber 2017a also draws on Sylvan's work in
non-classical logic to develop a "new version" of the Last
Man Example--the "Ultramodal Last Man"--with a
view to avoiding an alleged dilemma besetting the original Last Man
Example, "renewing a role for non-standard logics in value
theory".)


### 4.2 Deep Green Ethics



While Sylvan views the development of deep ecology sympathetically, he
distances himself from the positions being argued for under that
banner. His own "deep green ethics" is described most
clearly in Sylvan and Bennett (1994, ch. 5). Like deep ecology, the
position is, using the term originally coined in Naess (1973),
"deep" since it rejects the sole value assumption and
greater value thesis. But unlike deep ecology Sylvan rejects, in
particular:


1. biocentrism--"all and only life is valuable"



arguing instead that some non-living things have intrinsic value and
that not all life is intrinsically valuable; and


2. biospherical egalitarianism--"the equal value of all
life"



arguing instead for eco-impartiality, thus not valuing members of one
species over those of another simply on the basis of species
membership, and noting that evaluative impartiality with respect to
species does not entail their equal value. More generally, Sylvan
(1985) argues that under the strong West Coast US influence deep
ecology commits to an assortment of dubious metaphysical and
psychological themes--often leading to an anthropocentric
"person- and consciousness-oriented souffle". And
links to religion, in particular pantheism and nature mysticism,
threaten to "convert deep ecology into a new religion".
What results is a "deep ecology" that is
"conceptually murky" and subject to
"degeneration". As noted in Section 1, laying out these
points of difference with deep ecologists in uncompromising style
earned him the title 'the bad boy of deep ecology' (Orton
2005, Other Internet Resources). For responses, see Fox (1986) and
Attfield (1993).



His deep green theory is, following his metaphysical and logical
pluralism (cf. Sylvan 1997), also pluralistic "allow[ing] for
the requisite theory dependence and cultural relativity of
values" (1980a, 156), "there is no uniquely determined
correct value system ... there are various overlapping
systems" though he denies that ethical relativism follows from
this (Sylvan 1986, 13). He sees the ongoing cultural project of
developing an adequate environmental ethic as being in its early
stages.



Grey (2000) contends that the (proto)theory faces numerous problems;
for further analysis as to whether Sylvan's position has been
properly targeted see Lamb (2018, 565-80 passim).



Not content with mere theory, as noted in section 1, Sylvan also
engaged in ambitious practical conservation work, acquiring high-value
conservation properties for rehabilitation and protection. But the
value of such rehabilitated landscapes is contested in Elliot (1982)
and Katz (1992). Defending the idea that naturalness of origin is a
valuable aspect of wild nature, they argue that not only is restored
nature of lesser value than any wilderness that it replaces, but the
restored copy could be described as "a fake or a forgery"
(Elliot 1982, 84); restoration involves a "big lie" as
Katz puts it. Sylvan thinks they have grossly overstated their case
and responds in Sylvan (1994)--restored landscapes are not mere
artifact or fakery. They are not contrived gardens devoid of natural
values, artificial nature falsely presented as the real thing.



> 
> 
> Consider an area of restored bushland ... The restoration results
> primarily by nature doing its own thing; it is nothing like furniture
> or pottery making. An ecological restorer, unlike an artisan, does not
> produce the item, there is no making ... Rather there is
> adjustment at margins ... and there is *helping* in
> healing (Sylvan 1994, 68).
> 
> 
> 



Sylvan argues that Elliot and Katz have illicitly extended the notion
of an artifact, which is widely and wrongfully deployed in such
descriptions of restored natural areas and what they (especially Katz)
have failed to grasp is the value-enhancing role that restoration
plays in the many situations where the damage has already been done.
Such restoration "is an addition, an attempt ... to claim
back much more of what has [already] been grabbed and degraded or
ruined" (*Ibid.*, 75). In many cases restoration assists
nature in reasserting itself and taking control once more. What
results lacks certain properties of the original, to be sure,
especially natural continuity, but contributing to the restoration of
something to close-to-original value (as opposed to some low-value
fake) is, Sylvan argues, worthwhile and can result in near-natural
areas of enormous value. That is value enough.



Though Sylvan is uneasy using the term 'wilderness'
"due to its long history of unfavourable associations and
connotation", he agrees with the broader point being made by
Elliot and Katz--"ecological restoration is *not* an
alternative to retaining wilderness, to remnant wildernesses"
(Sylvan 1994, 75). However, they have overstated their case concerning
the value of restored landscapes. Elliot was persuaded, admitting that
he paid too little attention to the types of restoration that can be
achieved and underestimated the value and degree of naturalness that
can result. In a book-length response to Sylvan and other critics and
fellow travellers, Elliot (1997) clarifies his argument. Its Preface
acknowledged the enormous debt to Sylvan. He is, Elliot came to think,
quite right. "Mucking with nature" can result in something
of significant value and it is, Elliot argued, in many cases
obligatory to try to undo the damage we have done.



A further practical issue which Sylvan sees as requiring theoretical
justification is predation: the killing of animals for food.
"The vegetarian options face, it certainly seems, insuperable
difficulties, especially concerning such issues as animal predation
(which is an important, immensely frequent, and often
*desirable*, ecological fact), and concerning the reduction in
numbers of animals, especially introduced animals, which build up to
'pest proportions' (some reduction is often required for
vegetable growing to operate successfully)" (Routley 1982, 5).
Sylvan himself, for example, culled feral rabbits (a damaging,
introduced species in Australia) and he consumed the animals killed.
While his environmental ethic demands respect for intrinsically
valuable non-humans, he argues that the



> 
> 
> respect position is not a reverence position ... interference is
> acceptable [in certain cases] ... The lives, preferences,
> choices, and considerations of other species or objects of moral
> concern are not to be taken as sacred or inviolable [though we]
> require that good reasons be given for interfering with the
> environment (Sylvan and Bennett 1994, 149).
> 
> 
> 



See Routley (1982, SS4) for a defence (a paper which also presents
a moral defence of limited cannibalism). For a similar view see
Callicott (1980) and for defence of the contrary claim that we ought,
where possible, act to eliminate predation, even cases of wild animals
taking prey for food, see Nussbaum (2007, ch. 6).


### 4.3 Further Moral Theory



In addition to work in environmental ethics, Sylvan wrote on other
ethical issues including arguments for moral obligations to future
generations (cf. Routley and Routley 1978, Sylvan and Plumwood 1991),
and the ethics of energy choice (Routley and Routley 1979c). The
argument offered in the latter paper against nuclear power centres on
the (anthropocentric but nonetheless, in Sylvan's view, salient)
claim that bequeathing toxic nuclear waste to future generations
constitutes an ethically unacceptable shift of costs onto others. And
a similar argument was mounted against conspicuous consumption of
fossil fuels from what Sylvan and Plumwood then referred to as
"atmosphere heating" (Routley and Routley 1979c, SS3).
Theirs appear to be amongst the earliest philosophical discussions
focussing on the ethics of climate change. And it is not just the
claimed immorality following from the consequences of climate change
to future humans, though that is given weight; from a deep green
perspective, the claimed erosion of value outstrips mere
anthropocentric concerns and needs to take into account non-human
nature, where the resultant erosion of intrinsic value is taken to
loom large.



Considering destructive practices more generally, beyond those
destructive of the environment, Sylvan considered violence against
persons, arguing that not only was nuclear war immoral, but that which
conditionally promised it, nuclear deterrence, was also immoral (cf.
Routley 1984a). In fact, violence in general was, he argued, immoral,
defending pacifism and responding to the standard objections to it in
Routley (1984b).



In formal ethics, Sylvan defended a non-classical deontic logic.
Routley and Plumwood (1989) argued that the existence of moral
dilemmas establishes the need both for: (i) a non-classical
propositional logic underpinning deontic logic; and (ii) the rejection
of some other central principles of orthodox deontic logic, especially
the principle of deontic consistency



(PC)
\(\mathrm{O}A \rightarrow \twiddle\mathrm{O}\twiddle
A\)


and the Kantian principle ought-implies-can (since dilemmas create
impossible obligations). He argues that the sentential fragment of
deontic logic must be paraconsistent and a relevant logic is
recommended (see Section 2).



Sylvan saw his ethics as systematically connected with issues in
social and political philosophy, extending out from "deep green
ethics" to a broader "deep green theory" that
"includes a radical social and political theory, centred upon
social anarchistic forms of organization ... and elements of
radical economic theory ... There *have* to be changes in
social and political arrangements ... towards less consumptive,
populous and wasteful societies, and so on" (Sylvan and Bennett
1994, 151).



Some of these ideas are discussed at length in Routley and Routley
(1980b) where alternative forms of economic and political organisation
are first considered from an environmental perspective. Sylvan focuses
his attention on what he takes to be an evident failure of the
political arrangements proposed in the West. According to him, the
great limitations to the freedom of human beings, the uneven
distribution of wealth and, above all, the constant damages caused to
the environment are all symptoms of a disease that must be treated.
Sylvan argues for what he calls *pluralist anarchism*, (a form
of socialist anarchism) abandoning any form of government, including
the minimal one defended by Robert Nozick (2013).


### 4.4 Summary



Sylvan's work in moral theory helped pioneer the rise of
environmental philosophy as a new sub-discipline and connected
environmental issues with broader moral issues as well as issues in
political and social philosophy. Drawing on other work in metaphysics
and logic, he sought new non-anthropocentric moral foundations,
heavily critical of both traditional ethics and emerging alternatives
that lacked clarity and rigour.


## 5. Conclusion



The overall picture that emerges from Sylvan's work is of a
broad philosophy that draws on non-classical (relevant) logic, a
neo-Meinongian metaphysics and a neo-Meinongian value theory as a
means of accounting for "common-sense" ways of talking
(e.g., about things that do not exist), ways of valuing (e.g., the
seeming intrinsic value of things in the natural world) and
socio-political arrangements (e.g., a pluralist anarchism).
Sylvan's work was radical, but rigorous; a rich many-worlds
semantics underpins formal analyses. His work was contentious; many
traditional philosophical "problems" are claimed to be
artefacts of faulty orthodox theories. And his work was expansive;
philosophy's traditional role with the question "How are
we to live?" is taken seriously. Above all, Sylvan's
thought was unified and systematic: "What is sought is a theory
of values which blends both with object-theory and with deeper
environmental theory..." (1986, 1).



Sylvan's program was left unfinished when he died. Whatever one
thinks of his bold statements ("a wild mixture of wonderfully
incisive ideas and absolutely false claims," as Meyer put it in
1996), Sylvan pushes philosophers to recognize that many propositions
taken as facts are not unrestrictedly true, but rather are
*relative* to what assumptions one is making about logic,
ontology, and value. Changing those assumptions changes the
possibilities. And Sylvan's work urges us to be ready for more
possibilities--even what is, as he put it, "beyond the
possible" (this is the title of an unpublished manuscript cited
in Routley 1980).