Richard Sylvan [Routley]

First published Mon Dec 9, 2019; substantive revision Thu Jan 18, 2024

Richard Sylvan (born Routley, 1935–1996) was an Australasianphilosopher who was instrumental in starting major schools in: logic(especially paraconsistent and relevant logic), metaphysics(especially Meinongian ontology), and ethics (especially environmentalethics). In a large body of writing, Sylvan urged that, from logic toecology, we are not now thinking well about big problems—butthat we can and must do better. “Philosophers fiddle while theworld begins to burn,” he wrote (Hyde 2014, vi). In response, heproposed a highly ambitious and radical philosophical project ofre-evaluation, from foundations up, that has had ongoing impact inphilosophy (Casati, Mortensen & Priest 2018; Eckert (ed.) 2018;Hyde (ed.) 2019, and Weber (ed.) 2019).

Sylvan is known for proposing and defending some highly controversialviews, arguing in favour of inconsistent theories, non-existentobjects, and non-human values. Such unorthodox claims were especiallyunpopular in the time Sylvan was writing, in the latter half of the20^th century. But he thought it was vitally important, forphilosophy and for the world, that we take seriously ideas that runagainst conventions of the time. (As Robert Meyer put it, “Toget the counter-suggestible Sylvan to defend some view, one neededfirst to remark that the view was now utterly discredited”,Meyer 1996.) What were widely thought to be untenable positions, suchas Meinongianism, or failed theories, such as Cantor/Frege naïveset theory, attracted Sylvan’s attention for what he thought ofasrestoration:

A large part of my philosophical life has, so it appears, looking back(and also looking forward) consisted in rehabilitating abandonedphilosophical dwellings, habitats, and landscapes. (Preface, Sylvanms.Philosophical Rehabilitation, quoted in Hyde 2014,124)

His contributions are all systematically tied together in the serviceof a single project, around meaning and value, recognizing thelegitimacy and status of marginalized entities; for the landscapes hesought to rehabilitate had been, in his view,

laid waste or damaged by predecessors—too many of them, as thepredecessors adhered to an entirely defective set ofvalues…(ibid.).

He sought to make these philosophical landscapes viable by improvingthe way we reason about them, thereby casting them in a new light thatshowed their deep interconnectedness.

This entry will use the name ‘Sylvan’, even though he didnot begin using that name until 1983. All his work published beforethen uses his original name of ‘Routley’.

1. Life

Sylvan was born in 1935 in Levin, New Zealand. He received his MA inPhilosophy from the University of New Zealand (Wellington) in 1957 andthe following year completed a first-class Honours degree inmathematics there. His MA thesis, a 385-page work entitledMoralScepticism was given a mark of 95% by Arthur Prior, though helater commented that this was “not so much a mark as anexclamation mark” (quoted in D. Hyde, Introduction to Eckert(ed.) 2018, xiv). Blackwell agreed to publish a condensed version ofthe thesis but the required revisions were never undertaken.

In 1959, his teacher George Hughes then employed Sylvan to build asmall electro-mechanical computer capable of determining whether inputformulae were logical truths, logical falsehoods, orneither—with green, red and amber lights displaying therespective outcomes. He worked out how to build it from scratch usingrelays and uniselectors discarded by the post office and it was asuccess, but when run some years later it drew so much power that itblacked out the building it was housed in, ruining several experimentsin biology running in the building at the time. The Biology Departmentinsisted that it never be used again (Hyde 2014, 43).

In mid-1959, while bushwalking in Australia, he met Jack Smart (thenin Adelaide, later a colleague at the Australian National Universityand good bushwalking friend thereafter) who encouraged him to go toPrinceton for graduate work, as opposed to the then more usual choiceof UK universities like Cambridge. At Smart’s urging, “asa brash young man” Sylvan travelled to Princeton with aFulbright 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 MAfrom Princeton University but left before completing his PhD,dissatisfied with the intellectual climate there and subsequent lackof progress on his project. (He later received a PhD from Princeton in1980 for chapter one of Routley 1980.) He accepted a lectureship atSydney University in 1962 where he began lecturing undergraduates inlogic—introducing modern Russellian theory, displacing JohnAnderson’s long insistence on Aristotelian theory. There he metVal Plumwood (then Val Macrae, later Val Routley) and, in 1964, theymoved to the University of New England where Sylvan joined Len Goddardand a growing department—the first to have begun teaching modernlogic in Australia under Goddard in 1957. Goddard and Sylvan foundedthe first Australian Masters program in logic and formed theAustralasian Association of Logic, and with Len Goddard,David Londey, Ross Brady, Malcolm Rennie and Val Plumwood, hedeveloped what became known as the New England Group—working onnon-classical logic and paradoxes, among other things—butGoddard left a few years later, returning to St Andrews in Scotland.In 1967, with a year’s sabbatical owing, Sylvan and Plumwoodmarried (with Plumwood taking the name Routley) and they drove fromthe University to St Andrews to continue work with Goddard (traversingnorthern Australia, shipping the car from Darwin to Singapore, thenoverland into India and Pakistan, through the Middle East and EasternEurope). Upon return, in 1968, Sylvan took a position at MonashUniversity before being appointed to a Senior Fellowship in Philosophyin the Research School of Social Sciences at the Australian NationalUniversity (ANU) in 1971, where he remained for the rest of hiscareer. With only postgraduate students to supervise, his daysteaching undergraduates was at an end. A number of researchers fromthe New England Group subsequently joined him there and, with theaddition of Bob Meyer, Graham Priest, and others, a group re-formedaround Sylvan at the ANU—the well-known Canberra Logic Groupthat went on to pioneering research in non-classical, especiallyrelevant, logic. Through his contribution to the formation of researchgroups that were both innovative and productive, Sylvan influenced awhole generation of Australian philosophers and logicians. (For moreon 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 hehad purchased, and worked to conserve, five large tracts of richforest areas—four of which were subsequently bequeathed forconservation.

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

Within a year of arriving at the ANU (the centre of Australianforestry policy development), he and Plumwood became aware of plansfor extensive clearing of “useless” native forest for pineplantations across the country and so began work on a sustainedcritique 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 anuproar in forestry—with an attempt to suppress its publication(cf. Routley and Plumwood 1986). The repressive nature of theAustralian forestry industry was widely understood from within, withone forestry insider commenting, on receipt of a letter from Sylvanearly in the project, that: “for an Australian forester,receiving a letter from you is somewhat akin to a new Party membergetting a birthday card from Alexander Solzhenitsyn” (SylvanRSC, Box #45). Closer to home, they were also criticised by somecolleagues who, in the days before applied philosophy had come of age,saw their work as “propaganda” rather than scholarlyresearch. Despite resistance though, the book’s successfulpublication helped reform forestry in Australia, being subsequentlydescribed by a leading forestry expert as “monumentallyimportant” and “the most incisive and devastating economicanalysis of forestry … ever done in Australia” (Byron1999, 53). All three editions published through the ANU Press between1973 and 1975 sold out but by 1975 Sylvan was, remarkably, banned fromusing the ANU’s Forestry Department Library (the central storefor 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 “offgrid” into the temperate rainforest in the coastal ranges eastof Canberra where they began building a house from local stone (one offive houses that Sylvan built over his life). Working first from atent, then a shed, over the subsequent five years it took to build thehouse they produced much of their key work on relevant logic,neo-Meinongian metaphysics and environmental philosophy—oftendiscussing philosophy while building with graduate students and guestswho could be roped in to help. After a productive twenty-yearpartnership, Sylvan and Plumwood parted ways in 1983, and he marriedLouise Sylvan (née Merlin). That was also the year he changedhis name from ‘Richard Routley’ to ‘RichardSylvan’ while Val Routley, as she was then known, became ValPlumwood. Sylvan and Plumwood continued to work and correspond onclosely related themes in environmental philosophy untilSylvan’s death in 1996.

While his students and research assistants found him supportive andkind, Sylvan’s style sometimes offended his peers. He could bevery blunt in his assessment of other’s arguments and his shydemeanour and lack of small talk did little to counteract feelings ofrude-dismissal—friend and colleague Bob Meyer commenting that he“was a difficult man; not only did he fail to suffer foolsgladly, but he often disdained suffering them at all” (Meyer1996). Sylvan himself also commented, for example, that his“Critique of Deep Ecology” (Sylvan 1985) would “riskoffending many friends in the deeper ecology movement” (i) and,while he remained good friends with chief target Arne Naess, somewere, no doubt, offended. It earned him the title ‘the bad boyof deep ecology’ (Orton 2005, Other InternetResources)—still considered a “deep ecologist”despite the substance of his criticism concluding in his rejectingdeep ecology in favour of what he termed “deep greentheory”. Some who took offense on reading his response to theirwork would later go on to befriend and work with Sylvan, having gottenpast his blunt exterior. But with opposing-authority there was rarelyany rapprochement; his anti-authoritarianism was deep-rooted and hisanarchist tendencies manifest—in both academic work and in hisbehaviour.

His publishing habits also drew attention. Seeking an outlet forlonger papers and essays in the late 1970s, and wary of“profiteering” publishers, in the do-it-yourself spiritthat infused much of Sylvan’s life he began publishing a numberof pre-print series in the Research School of Social Sciences where heworked at the ANU. Beginning with work of the Canberra Logic Group,the “Yellow Series” (as it became known) included overtwenty publications by Group members between 1978 and 1985. Therefollowed other Series including work in logic, metaphysics, thephilosophy of science and much of his own work in environmentalphilosophy. In total, there were over fifty such publications of whichover half were Sylvan’s own work. The publications ranged fromtens of pages to hundreds and could be purchased by post from thedepartment for a few dollars. The largest, at just over one thousandpages (Exploring Meinong’s Jungle and Beyond), forexample, was available in hardback for $10. Such anomalous publishinghabits meant that a considerable amount of his work is now very hardto access (though, in some cases, republication through more usualchannels 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 Balito discuss Hindu philosophy with priests there. (For more details, seeHyde 2014.)

2. Logic

This section describes Sylvan’s work in logic. As in other areasof his philosophy, Sylvan was notable for his staunch defence ofhighly controversial and radical views—most strikingly, thatclassical logic is wrong, that non-classical logic is right, and thatsome contradictions may betrue (see: dialetheism). Whatmakes his work worth remembering is that he backed up such claims withrigorous (if contentious) arguments and mathematical details.

Sylvan’s work in logic can be viewed in part as a response to awide range ofparadoxes, such as the paradoxes ofself-reference (like the Liar Paradox). He was equally focused onparadoxes of implication, and so was a leading developer ofrelevant logics, logics characterized by their concern thatthere be a meaningful connection between the antecedent and consequentof a conditional. These topics would lead him to be one of thefounders of the so-called “Australasian school” ofparaconsistent logic, logics that tolerate inconsistencywithout incoherence (Hyde 2014, 71 and see the entry onparaconsistent logic). He was perennially concerned with theuniversality of logic. Along with intrinsic interest, hislogical research was always motivated by its eventual application toissues in metaphysics, ethics, and beyond.

2.1 Early work

This section describes Sylvan’s work in neutral quantificationtheory and significance logics. In both cases, he is concerned withgranting legitimacy to otherwise discredited or rejectedentities—the existence (or lack thereof) of objects that seemlike perfectly good subjects of quantification in apparently truesentences; and the status of “nonsensical” sentences thatseem like they are essential parts of good reasoning.

2.1.1 Quantification

From his earliest days at Princeton, Sylvan had argued that anadequate philosophy of science required quantification overnon-existent objects (numbers, frictionless planes, etc.), and anadequate semantics for fictional discourse was also best pursued alongthese lines. (Cf. Routley 1965, 1966a, 1979a; Routley and Routley1973b, 1979a.) For reasons discussed in Section 3 below, he followedMeinong in seeking a theory that includes non-existent objects, and alogic that can handle such objects.

A basic idea here (e.g., in Routley 1980) is to reassess the status oftheexistential quantifier: $\exists$. It is commonplaceamongst logicians, especially since Russell 1905 and especiallyQuine’s article “On What There Is”, to read this asontologically loaded; so if $\exists x Ax$ is true thensome $x$ exists and has property $A$. Sylvan urges that wedistinguish betweenparticular claims (‘some $x$ is$A$’) andexistential claims (‘anexisting $x$ is $A$’). With the latter existentialreading, it is impossible to claim that some things just do not exist;that amounts to saying something both exists and does not exist, so itexists after all. But with the formerparticular reading, theclaim ‘some things do not exist’ comes out as intended,with its apparent natural language meaning. Because the existentialinterpretation of the backward ‘E’ symbol has becomehopelessly entrenched, Sylvan introduced new symbols, ‘P’(for particular) and its dual ‘U’ (universal), to act asneutral quantifiers. Thus the logical ground was laid forsubsequent work in neo-Meinongian metaphysics (cf. Section 3).

This work, both the metaphysics and logic, led to a number of debateswith David Lewis. Lewis (1990) argues that the apparently deepdisagreement Sylvan has with ontologically loaded quantification mightbe dispelled by a translation manual, between his unconventionalMeinongian reading and a conventional one (cf. Priest 2005, Section7.9.):

when [Sylvan] says ‘is an object’ this can be replacedby ‘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 littlemore than quibbling about the use of the word ‘exists’when it comes to abstract objects. But Lewis is self-critically awarethat any misunderstanding may be mutual, and cautions that

To suppose that [Sylvan] mistakes mere terminological difference forprofound philosophical disagreement is to accuse him of stupidity farbeyond belief (Lewis 1990, 30).

Worry about communication difficulties between classical andnon-classical logicians would be voiced by Lewis again, eventuallydeclining 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 firstinstances of Sylvan pursuing the development ofnon-classicallogics as a response to a range of paradoxes. A preliminaryaspect to this work was the investigation of the fundamental notion ofsignificance.

Especially in early 20^th century philosophy, a popularmeans of dismissing various philosophical theses (say in metaphysics)was “on the grounds that they are nonsense, nonsignificant,absurd, meaningless, unintelligible, or logically odd” (Goddardand Routley 1973, 1). Such rejections are characteristic of logicalpositivism, taking a cue from Wittgenstein’s accusation thatmuch of philosophy is “not false, but senseless[unsinnig]” [Tractatus 4.003] and thereforeeasy to ignore. By the late 1960s, it seemed to Routley and Goddardthat Russell and others had succeeded in promoting a“meaninglessness” solution to various paradoxes like theLiar sentence, or the Russell contradiction,

the set $R$ of all sets that are not members of themselves is amember of itself if and only if it is not a member of itself

According to various Russell/Tarski type theories, sentences areregimented to levels of a hierarchy and restricted in scope about whatthey can express; then liar-type sentences are, on this sort ofsolution, “nonsense”. Appeal to non-significance is thenmeant 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 thatphilosophers have been too eager to condemn theses that “areneither gibberish nor ungrammatical” (4).

In response, Routley (1966b), Brady and Routley (1973), and Goddardand Routley (1973) argue for a logic of significance for the formalstudy of significance. The ideas here can be summed up in threetheses.First, there are grammatically correct naturallanguage sentences, containing only recognized vocabulary (say ofEnglish), which “are held to be meaningless” (Goddard andRoutley 1973, 2); but “unlike seriously ungrammatical sentences,[they] can figure in valid arguments and can occur as unquotedcomponents of grammatical sentences” (Routley 1969, 367).Second, such sentences require a non-classical andspecificallythree-valued logic. Meaningless sentences stillmust have some recognizedstatus—and it is some statusother than ‘true’ or ‘false’ (See Haack 1971,1975, and Bradley 1978 for alternatives). As Brady and Sylvan putit,

We believe that the deep structure of natural languages, and hence ofthe languages in which philosophical problems are characteristicallyformulated, will have to be based on an enriched significance logicwhich has a third value—nonsense or nonsignificance—andnot on a classical two-valued logic which only has truth and falsityas its values (Brady and Routley 1973, 211).

Third, all significance logics will need to be based on acommoncontext logic, where a fixed context of use orcircumstance determines the ‘significance principles’ ofeach logic (Cocchiarella 1984; cf. Ripley 2012, 101).

Sylvan and Goddard want a logic that can track (as opposed to simplydeny) non-significant sentences, which we may think of astruth-value gaps. Their proposed logic of significance may beunderstood (see Szmuc and Omori 2018) as being based on a three-valuedlogic,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 beread as, not a truth-value, but rather as a kind of meaninglessness.These matrices respect two basic conditions laid down in (Goddard andRoutley 1973, 260), that

in the case of classical truth values $t$ and $f$, the tablesjust are those of classical logic, so that this is a generalization ofthe classical case
any sentence with a non-significant component itself becomesnon-significant

An argument isvalid on this logic iff there is no evaluationthat interprets all the premises as true (value $t$) but theconclusion untrue (values $f$ and $n$). This logic was furtherinvestigated by Brady (1980) and Bunder (1979, 1980a, 1980b). Forcriticism, see Lambert (1968) and Haack (1971, 1975).

This early work is transitional. Paradoxical sentences at this stageof Sylvan’s thinking may have a value, but certainly not that of‘true’ (or ‘false’). This relativelyconservative attitude would begin to fall away as his thinkingdeveloped.

2.2 Relevant and Paraconsistent Logic

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

2.2.1 Universality

In 1975 Sylvan took up the idea of auniversal semanticsdirectly (although the title of his paper “UniversalSemantics?” is in the uncertain form of a question). Inspired byrecent advances in Montague grammar and categorial languages, hebecame speculatively interested in whether there is some common formbeneath all natural languages, that could be adequately representedthough logical symbolism. Specifically, he was interested in some“leading assumptions” of the time, namely (1975, 327):

that the surface structure of a grammar can be transformed, ortranslated, or reduced, into a “deep structure”; and
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 belambasted most vociferously with Meyer in their paper“Extensional Reduction” of 1977), and the uses of worldssemantics to do it.

As an initial gloss, auniversal semantics, whatever else itmay be, is intended to be a framework able to express everything thatcan be expressed. As in Section 2.1, there should not be anyartificial constraints placed on what we might be able to reason wellabout (or, by extension, think about or imagine), nonsense or not. Anda universal logic shouldnot have, as theorems, anything thatis patently incorrect. Putting these two ideas together, Sylvan wasalready convinced that “classical logic” is too strong toserve as the basis for any universal semantics, because itcannot express everything that is expressible, such as manyintensional notions; and itdoes deliver apparentlynonsensical theses such as the paradoxes of material implication (seeSection 2.2.2 below). (These two aspects of a logic—the extentof the class of models it can describe, and the set of validities ityields—are inversely proportional; cf. Priest 2008,36–7.)

On these grounds, Sylvan looked increasingly at non-classical logicsas a better framework or foundation for any universal semantics. His1977 manifesto “Ultralogic as universal?” (see Ficara2023) introduces the titular subject (note again the question mark) asfollows:

A universal logic, in the intended sense, is one which is applicablein every situation whether realised or not, possible or not. Thus auniversal logic is like a universal key, which opens, if rightlyoperated, all locks. It provides a canon for reasoning in everysituation, including illogical, inconsistent and paradoxical ones. Fewprevailing logics stand up to such a test. … [A] universallogic should be adequate for mathematicaland philosophicalpurposes—and also for logical functions in other areas such asbiology, economics, astrology, theology, and so on (893).

Approaching any universal logic, according to Sylvan, would requireextending the expressive power of classical logic, and concomitantlyrestricting its proving power.

Two possible misinterpretations of this “universalist”project should be flagged. First, Sylvan did not argue that somespecific alternative logic is the absolutely correct one, or even thatthere should be one and only one correct alternative (see Section3.3). Second, although he can sound rhetorically partisan andideological, Sylvan’s approach was ultimately rather pragmatic:he couched theory choice in practical cost/benefit analyses familiarfrom conventional philosophy of science (Routley 1980a). On themeaning of ‘universality’ in this context see Mares (2019)and Nolan (2018). Brady’s 2006 book takes its title in part fromSylvan’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 theproject of refining C.I. Lewis’sstrict implication toovercome various paradoxes of the conditional. (See the encyclopediaentry onindicative conditionals.) For, according to the classicalaccount of material implication $\supset$, for any three randomdeclarative sentences $p$, $q$, $r$ you find on the Internet, $(p \supset q) \lor (q \supset r) $ is valid (to take just oneexample; see Routleyet al. 1982, 6–7). One diagnosisof the problem here is that all these conditionals, of the form‘if $p$ then $q$’, displayirrelevance: theantecedent $p$ need not have anything “to do with” theconsequent $q$, whereas correct natural language conditionals (sothe argument goes) always respect some kind of relevant connection.The problem may be resolved by turning to an appropriate relevantlogic. (See the related entry onrelevance logic.)

Sylvan is explicit, though, that his “main concern is not reallyrelevance at all—the appropriate sort of relevance is aby-product of any good implication relation, which comes out in thewash” (Routleyet al. 1982, x) after a deeper diagnosisof the paradoxes. He emphasizes that what is really at issue for asuccessful account of a conditional isabsolutesufficiency—that when $p$ really does imply $q$, thismeans that $p$ is all that is needed for $q$.

The central deducibility relation of ultramodal logics, entailment, isintended to capture the notion of sufficiency … of theantecedent of an entailment on its own, without any additionalimported truth, especially imported logical truths. …Sufficiency is a go-anywhere notion, which is not limited by the factthat the situation in which it operates is somehow classicallyincoherent, e.g., inconsistent or paradoxical. If $A$ is sufficientfor $B$ then it does not matter what else goes on; logical laws maygo 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). Insome otherwise highly critical remarks, Burgess (1983, 45) writes that“Routleyanism and Andersonianobelnapianism are so dissimilarthat it is misleading to apply a single label‘relevantism’ to both. (And indeed, [Sylvan] sometimesadopts a different label.)”

The diagnosis of the paradoxes of implication as failures of respectfor sufficiency leads naturally to an alternative path to theirresolution, of a piece with Sylvan’s concerns aboutuniversality. On this view, the paradoxes of implication are symptomsof takingtoo few possibilities into account. One may thinkof classical material implication as taking onlyonesituation 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 soqmaterially 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 oftwo 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 inevery 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 whichp holds withoutq and vice versa, showing a failure of sufficiency exactlybecause more worlds are considered.

The key to solving the paradoxes and approaching universality, on thisapproach, is to broaden the collection of worlds, in order to sieveout what sufficiency relations persist. Sylvan extends this strategyto 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., atevery world in which $p$, also $p$, then to show that arbitrary$q$ is not sufficient for this self-implication, there needs to be acounterexample: one where $q$ holds without $p \rightarrow p$.Generally, to preserve sufficiency, the same strategy goes for anylogical truth, $B$: if we are to avoid $A \rightarrow B$ when$B$ is logically necessary but irrelevant to $A$, there must bepoints at whicheven logical truths fail. For example, therewould be a world at which the law of non-contradiction $\twiddle (A\amp \twiddle A)$ fails. These points are known as non-normal orimpossible worlds, about which there is a growing literature (e.g.,Nolan 2013; Berto and Jago 2019).

The logics being proposed here, then, are naturallyparaconsistent: they do not validate the “spread”law: ($p \amp \twiddle p) \rightarrow q$, and so can putativelyhandle inconsistency without collapse into triviality. (InSociative Logics, Sylvan refers to these aspararelevant logics.) Indeed, with counterexamples to the lawof non-contradiction, there would be worlds where some sentences areboth true and false.

The first relevant logics were presented proof theoretically, in termsof axioms and closure under rules. The need for a model theoreticinterpretation (given in a classical metatheory) resulted inSylvan’s co-development with Plumwood of ternary relationsemantics for first degree entailment relevant logics (Routley andRoutley 1972) and the ensuing Routley-Meyer partnership that provedand extended a range of results for relevant logics (cf. Routley,Meyer,et al. 1982; and Brady 2003). (Cf. Fine 1974; Urquhart1972.) ARoutley-Meyer frame $\langle W, N, 0, R, {}^*\rangle$ consists of:

a set of worlds $W$,
among which are the normal worlds $N$, the others beingnon-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 theRoutleyStar.

An evaluation then assigns formulas a truth-value at each world; sosome $p$ may be true at one world but false at another. With theRoutley star, these may even be the same world. The conditions onimplication 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 someworlds; indeed, respecting relevance demands it. These conditions canbe seen asgeneralizations of more standard ones: in the caseof implication, if $y = z$ then this is just a modalized materialconditional in a Kripke frame; in the case of negation, if $x = x^*$then this is just the clause for negation in classical logic. Forfurther details, see the entry onrelevance logic, Mares (2004), and Priest (2008, ch. 10). On the Routley star seeRestall (1999).

Routley/Myer semantics has generated an enormous secondary literature(cf. the secondary literature section of the bibliography), forexample Copeland 1979, 1983, Thomas 2015. Debates have surrounded: theinterpretation of the semantics (e.g., the ternary relation, theRoutley-star operator, non-normal worlds); alternative semantics forrelevant logics; the adequacy of non-classical responses to semanticand set-theoretic paradoxes; dialetheism; and naïve set theory.For recent work about the ternary relation see Beall et al 2012; for arecent 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 toaccount for implication led to tentative endorsement of thepossibility of true contradictions (dialetheism). Most relevantlogicians thought of these “worlds” merely as artefacts ofthe semantics, not as legitimate possibilities(indeed—they’re impossible!); but there the idea was, of“dialectical” or contradictory worlds. By (1976), he andMeyer consider a rather literal interpretation of Hegelian dialectic,and openly question the “Consistency Hypothesis” that theworld is consistent. They urge instead a “dialectical”possibility. They present the (relevant) logicDL (fordialectical logic), and give it an axiomatization that explicitlyincludes an outright contradiction $p \amp \twiddle p$ as anaxiom. (Smiley calls this “Routley and Meyer’swar work” (Smiley and Priest 1993, 17). See also van Benthem1979, Havas 1981, Ficara 2021.)

When Graham Priest arrived in Australia and presented his ‘Logicof Paradox’ to the 1976 meeting of the Australasian Associationof Logic, another intensely productive partnership was struck. Withtrue contradictions—later to be nameddialetheia bySylvan and Priest—in view, the potential of surpassing classicallogic opened up:

The liberating effect of giving up the classical faith … isimmense: … one is free to return to something like the grandsimplicity of naive set theory, to semantically closed naturallanguages (having abandoned the towering but ill-constructed andmostly unfinished hierarchies of formal languages), and to intuitiveaccounts of truth, of proof, and of many other intensional notions(1979b, 302).

Dialetheism, especially due to Priest, has prompted a long and growingdiscussion (see Priest 1987 [2006] and Beall 2009 for defences ande.g., Field 2008 for some useful criticism; see the bibliography inthe entry ondialetheism for more).

Sylvan’s thinking about contradictions evolved, depending on hisco-author, even over the course of a book. InRelevant Logics andtheir Rivals (1982), early chapters float dialetheism as ahypothesis, in an “agnostic” spirit (61), or that oftaking precautions; whereas later in the book, it states bluntly that“mathematics is inconsistent” (255). (The shift iscriticized 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 tounderwrite inconsistent but non-trivial mathematical and scientifictheories, which had been of interest to him since the start. Ofparticular note is naïve set theory, used by Cantor, Dedekind,and Frege in the foundations of mathematics (see the entry onthe early development of set theory), but dealt an apparently fatal blow by Russell’s paradox circa1900. Building from work by Brady (1971), naïve set theory asformulated with the implication connective‘$\rightarrow$’ ofDL (or the slightlyweakerDK) takes as axioms that there is a set for everyproperty $A$, i.e.,

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

where ‘$\in$’ is read ‘is a member of’ andwith 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 andextensionality, in Routley (1977) he begins to sketch outwhat he hopes will be the “rehabilitation” of naïveset 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. Theparadoxes, in other words, areproofs, and the resultingcontradictions aretheorems (1979b, 302). Sylvan sketches thefurther work needed to show that elementary principles such as theZermelo-Fraenkel axioms and their immediate consequences can bederived. And he speculates, much more ambitiously, that the Axiom ofChoice and the Continuum Hypothesis could be decided as well; seeWeber (2012). Priest 2006, chapter 18 is a discussion ofparaconsistent set theory in this tradition.

The project was given an essential boost when Brady confirmed thenon-triviality of the theory in the late 70s, i.e., that there are(absurd) sentences thatcannot be proved in this theory,results which appeared as Brady (1989); see (Brady 2006). Further workin relevant arithmetic, by Routley, Meyer, Mortensen, Dunn, Priest,Restall, and others, followed. This led to the area now known asinconsistent mathematics, carried forward especially byMortensen (1995, 2010), where e.g., the Routley star is used as afunctor to great effect; see the entry oninconsistent mathematics for further references, and Weber 2022.

Sylvan saw relevant logics as only one type of what he termedsociative logics, logics that require some meaningfulassociation or connection between premises and conclusions of validarguments, or antecedents and consequents of valid implications. Alongthese lines, he contributed to the development ofconnexivelogics, systems that include principles like so-calledAristotle’s thesis, $\twiddle (A \rightarrow \twiddle A)$.Standard relevant logics and non-classical logics more generallyusually only deny some classically valid principle. Connexive logicsare in some ways even more radical than relevant logics, because theyarecontra-classical—e.g. since Aristotle’sthesis is invalid according to classical logic. See the entry onconnexive logic and Sylvan 2000a.

2.3 Applications

This section mentions briefly some other applications ofSylvan’s preferred logics to a wide range of philosophicalproblems. Sylvan saw applications as a test for the choice of suchtheories over rival logics. Sections 3 and 4 are in a way extendeddiscussions of such applications. Sylvan argued that relevant and,more broadly, what he termed “sociative logics” hadapplications in areas as diverse as causation, an analysis ofknowledge, vagueness (including the idea that there are vague objects;see Sylvan and Hyde 1993), and value theory. Here we sketch two suchapplications, in confirmation, and computation.

2.3.1 Confirmation

Following Goddard (1977), Sylvan (along with Nola, in 1991) appliesrelevant logic to solve theparadoxes of confirmation madefamous by Hempel. These are problems in philosophy of science aboutformulating inductive generalizations such as

All ravens are black,

which is confirmed by instances of things which are both black andravens; but the universal generalization is logically equivalent toits contrapositive form

All non-black things are non-ravens,

which would similarly be confirmed by any non-black non-raven; butsince e.g., a red pencil is obviouslynot confirmation thatall ravens are black, something has gone wrong. For Sylvan, theproblem—as is often his diagnosis—lies in theformalization of the natural language claims—“It iswell-known in relevance circles that the most outrageous of theseparadoxes are automatically removed by replacement of the materialconditional …” (2000a, 227). “A relevanceshift,” he argues with typical restraint, “is a sure-fireway 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 ofrecursion theory, towards a non-classical theory of computation (cf.Copeland and Sylvan 1999; Sylvan 2000a). According to work by Turing,Church, and Gödel in the 1930s, computers face logical limits onwhat they can compute (see the entry onThe Church-Turing Thesis and the entry oncomputability and complexity). Uncomputability proofs, though, bear a very strong resemblance to thederivations of Russell’s paradox and other diagonalparadoxes. If “dialectical” logic can be used to solvethose paradoxes, though—essentially, by accepting that they havetruly contradictory conclusions (see Section 2.2 above)—thencould the same be done in the case of computers? Then the conclusionwould be,not that there are uncomputable algorithms, butrather “there are more algorithmic functions than allalgorithmic 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 inmetaphysics and ethics: a polemical rebuke of the perceived powers ofthe day—in the case of logic, the hegemony of classicallogic—and a highly imaginative and open-minded attitude towardswhat sorts of entities—possible and impossible alike—ourbest theories should condone. We turn now to these other aspects ofhis work.

3. Ontology and Metaphysics

In this section, we present Sylvan’s work in ontology andmetaphysics. As discussed below, Sylvan was deeply inspired by AlexiusMeinong but, as a matter of terminology, their understanding of‘ontology’ and ‘metaphysics’ differ: whileMeinong would situate metaphysics and ontology as small corners withina more general object theory, Sylvan situated them the other wayaround. (See, for instance, Meinong 1904, §2 and §11; Sylvan1995a, 47). In what follows, we follow Sylvan and employ what we taketo be contemporary standard usage of ‘ontology’ (roughlyunderstood as the study of what exists and what does not) and‘metaphysics’ (roughly understood as the study of thestructure of reality), while acknowledging that Meinong-scholars mightdispute this use of terms. In Section 3.1, we sketch some of theessential features ofnoneism, that is, Sylvan’s theoryabout non-existent objects. In Section 3.2, we discuss Sylvan’sattempt at expanding the horizons of traditional ontology bydeveloping a new theory calledsistology. Finally, in Section3.3, we summarize Sylvan’s heterodox account of pluralism,labelledplurallism.

3.1 Noneism

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

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

Sylvan’s intuition is that, in order to be able to say somethingtrue about non-existent items, we need to allow for the possibilitythat non-existent items have properties. For instance, in order to beable to say that ‘Sherlock Holmes is a detective’ is true,Sherlock Holmes needs to have the property ofbeing adetective. Now, according to Sylvan, a suitable philosophicalbackground for supporting this intuition is Meinong’sTheoryof Objects. For this reason, inExploring Meinong’sJungle and Beyond (Routley 1980), Sylvan tries to deliver amodern logical presentation of Meinong’s philosophy. Hewrites:

Meinong’s theory provides a coherent scheme for talking andreasoning about all items, not just those which exist, without thenecessity for distorting or unworkable reductions; and in doing so itattributes … features [properties] to nonentities [non-existentobjects] (1980, iv–v).

At nearly 1000 pages, Routley (1980) develops noneism in great detail.We summarize it in five main theses, which represent the coreassumptions of what Sylvan callsminimal noneism (from now onMN). First of all, following Meinong’s accountof intentionality, Sylvan believes that:

(MN₁): “everything whatever (…) is an object [anitem]”

(1980, 1–2; 352). In other words, every time we refer tosomething, we refer to an item. If I tell a story about SherlockHolmes, I tell a story about an item, namely that item that is thesubject 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 itemsexist (e.g., the Eiffel Tower) and some others do not (e.g., SherlockHolmes). Like Meinong, Sylvan treats existence as a property: someitems have the property ofbeing red and some other items donot; some items have the property ofbeing existent (e.g.,the Eiffel Tower) and some items do not (e.g., Sherlock Holmes). Whenitems do not have the property ofbeing existent, they arenon-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 oranother”

(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’sindifference principle: theproperties an item has are indifferent to the ontological status ofthe item itself. Thesis(MN₄) correspondsto Meinong’sindependence principle: an item’shaving properties is independent of whether the item inquestion exists or not.

As many have pointed out (cf. Russell 1905 and 1907; see also Berto2013 and Priest 2005), the original theory defended by Meinong facesproblems. In particular, Meinong’s theory is threatened bytriviality (Berto 2013, 106–107); that is, thesituation in which everything exists—including items thatclearly do not. E.g., if I refer to not just to Sherlock Holmes but to“theexisting 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 andnon-characterizing properties. The former are necessary in order todefine the essence of an object. A characterizing property is aproperty (e.g.,being a detective orbeing smart)that is necessary in order to make a specific item (e.g., SherlockHolmes) the item that it is. Using Sylvan’s words:

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

On the other hand, the non-characterizing properties are all thoseproperties that are not characterizing. According to Sylvan, theproperty ofbeing existent is a non-characterizingproperty.

As it has been extensively argued in the secondary literature (see,for instance, Priest 2005), the difference between these two kinds ofproperties is unclear. It is also fair to say that, even though some(neo-)Meinongians have tried to cash out such a distinction in moreprecise terms (see, for instance, Jacquette 2015 and 2017; Parsons1978 and 1980), there is little consensus that any progress has beenmade. That being said, even though it is certainly difficult to havestrict criteria to separate the characterizing properties from thenon-characterizing ones, it is absolutely clear that:

(MN₅): “neither existence nor non-existence is a characterizingproperty”

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

The second move Sylvan makes in response to the triviality problem isrepresented by the idea that, even though it is the case that everytime we refer to something we refer to an item, the item in questionhas characterizing properties. Following Berto (2013), we can also saythat, consistent with some other neo-Meinongians (i.e., Jacquette2015; Parsons 1980), Sylvan argues in favour of the followingcharacterization principle:

for any set ofcharacterizing properties, some item satisfiesit.

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

As we have already specified above,minimal noneism is merelythe core of Sylvan’s noneism which is more elaborate andsophisticated than sketched here. Exactly because of its complexity,noneism forces us to rethink some of our traditional approaches toimportant philosophical topics. Examples are intensionality,nonexistence, impossibilia, and paradoxicality. Moreover, in the lightof these conceptual innovations, Sylvan also discusses some of therelevant 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 offiction (cf. 1980, 537–595).

Sylvan spent many years developing and defending noneism, but he wasnot entirely satisfied with it. He had two major complaints. On theone hand, he thought that his way of presenting noneism wasrhetorically problematic: EMJB was too long, rambling, and notincisive enough. As such, EMJB needed to be rewritten (see Sylvan1995b). On the other hand, he aimed at “liberalizingnoneism” by allowing all items to have both characterizing andnon-characterizing properties (Sylvan 1995b). Archival documents showthat, to this end, Sylvan tried to develop a new theory that has manyfeatures 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 onehand, sistology adopts all the fundamental ideas of noneism. Likenoneism, sistology includes items that do not exist (cf. Sylvan 1991,837; 1997, 11–12) and it accepts that those items haveproperties (cf. 1991, 838–39). On the other hand, sistologydevelops and enriches noneism in the following ways.

To begin with, Sylvan tried to move the focus of his attention fromthe existence (or non-existence) of items to theirbeingitems. Using Sylvan’s words, sistology is concerned with“all items ashaving standing” (1991, 838). Thus,sistology aims at casting a new light on what it means tobe anitem instead of showing that it is possible to have non-existentitems. The latter project was the unique task of noneism.

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

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

In particular, Sylvan devoted significant effort to this last clusterof items, underscoring the idea they require the employment of aparaconsistent logic. Given that inconsistent items have inconsistentproperties, if classical logic is employed then triviality immediatelyfollows. In order to avoid trivialism, the adoption of aparaconsistent logic is required.

Consider, for instance, inconsistent objects. (…) By virtue ofwhat they are, they have contradictory properties, therebytrivializing any theory built upon mainstream logic. An authenticsistology requires logical reformulation of a more demandingparaconsistent type (Sylvan 1991, 839).

The third and last attempt to develop noneism is represented by aserious engagement with the notion of a “source”. As hehad already discussed, a “source” is what allows us tounderstand the charactering properties that an item (cf. 1980, 463;1995a). The source of Anna Karenina’s characterizing propertiesis Tolstoy’sAnna Karenina. In sistology, Sylvan aimsat deepening our understanding of sources by admitting that not all ofthem are equally reliable. For instance, optical illusions teach usthat visual perceptions are not always a trustworthy source forcharacterizing the items we see. For this reason, Sylvan suggestsintroducing two kinds of predicates. The first kind (call them“ordinary predicates”) tell us how items look;the second kind (call them “non-ordinarypredicates”) tell us how items really are.

Not all sources are always reliable or otherwise satisfactory; forexample, perceptual sources are notoriously unreliable as to howthingsreally are. (…) Thus, [the] division of[ordinary and non-ordinary] properties is presumed (1991, 839; italicsours).

Sistology, which is only sketched by Sylvan, nevertheless anticipatessome of the ideas currently debated among neo-Meinongians, forexample, as discussed above, with “items in general”.Regardless of the existence or non-existence of these items, sistologyconcerns their “having standing” (1991, 839). In so doing,Sylvan focuses his attention on one of the most under-researchednotions of Meinong’s theory of objects, that is, the so-calleddoctrine ofOutsidebeing [Aussersein]. Only recentlyhave neo-Meinongian started to turn their attention to this topic(Casati and Priest 2017; Grossman 1974; Jacquette 2015). So too withthe very particular kind of object that is “nothingness”(cf. Sylvan 1995a). After a long-standing lack of interest in thesetopics, neo-Meinongians have begun to take them into seriousconsideration as well (Casati and Fujikawa 2019; Priest 2014a and2014b; Jacquette 2013).

3.3 Plural(l)ism

In the current philosophical landscape, there are many different formsof pluralism on offer. For instance, there is anontologicalform of pluralism (there are different ways of being),truthpluralism (there are different ways of being true), and there is alogical form of pluralism (there is more than one correctlogic; see the entry onlogical pluralism). However, it is almost universally assumed, if mostly unstated, thatthere can be no pluralism about theactual world—thisone is the onlyactual one. As should appear clear from thisentry, though, Sylvan was accustomed to challenging the philosophicalconsensus. He began by attacking classical logic, he continued byquestioning the so-called Ontological Assumption and, late in hiscareer, he decided to challenge what he callsone-world-ism,that is, the idea that there is only one actual world. (For anotherexample of a philosophical position which considers a plurality ofactual worlds, see Goodman (1978).)

Sylvan argues that there is a plurality of actual worlds we all livein. In hisTranscendental Metaphysics (1997) he claims:

A theme, to be defended at length, is that while there isanactual world, which is suitably external, mind-independent,perceiver-independent, and the like, it is not unique.There aremany actual worlds. That theme is bound to strike others, as itstill 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 theothers, he refers to his own theory with a neologism:plurallism. The aims of such a theory are summarized asfollows:

The overarching themes of plurallism are (…): (1)There isno 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 ofarguments.

Sylvan arguesindirectly there is a lack of (good) argumentsin favour of the uniqueness of the actual world. From the fact thatthere is such a thing as an actual world it does not necessarilyfollow that such a world is unique, nor is its uniqueness observable(cf. 1997, 54–60).

On the other hand, hedirectly supports plurallism by arguingthat for each area of research, there is (or there could be) aplurality of correct theories. His reasoning goes as follows. Alltheories are grounded on logic because logic is necessary forreasoning about both the data used by those theories and the theoriesthemselves. And, if there is, not just one, but aplurality ofcorrect logics, there is (or there could be) a plurality ofcorrect theories which spring from all those different, but allequally acceptable, ways of reasoning as well (cf. 1997, 61–74).From this, a plurality of actual worlds follows if we accept twoenthymematic assumptions. The first one is that any correct logic, invirtue of its being correct, properly describes an actual world. Ifso, if there is more than one correct logic, there is more than oneactual world too. The second assumption, then, is that there are manycorrect logics. This idea was not shared by Sylvan’scontemporaries but one that he came to defend late in his career,claiming (1997, xix) “that not merely is there a plurality oflogics, but there is also [a plurality] of correct logics”. Theidea is elaborated on in Sylvan (1997, ch. 4) and is now widelydiscussed in the literature (see, for instance, Beall and Restall2000; Russell 2008; Weber 2017b). Sylvan claims that phenomenologicaldata seems to support plurallism as well (cf. 1997,118–133).

Sylvan’s motivations for developing plurallism are not uniquelyphilosophical. On the contrary, he believes that the existence of theplurality of actual worlds can have important political consequencestoo. One of those consequences is the extension and strengthening ofour idea of tolerance. According to Sylvan, intolerant behaviours areoften, if not always, grounded on ideologies driven by what he callsthe “one-true-way” (1997, 462) or the“one-admissible-way” (1997, 462). Governments,religious groups, and even scientists believe that “truth shouldbe imposed” (1997, 462) where truth is what isuniquelydetermined by them. Plurallism invites us to entertain the idea that,as there is no such thing as a unique actual world, there is no suchthing as a unique truth. And this should undermine the ideologicalroots of intolerant behaviours.

3.4 Summary

In many ways, Sylvan’s philosophical and logical research isdevoted 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 differentlogics, all sorts of items, and a plurality of actual worlds couldpeacefully 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 onenvironmental ethics Section 2) was, alongside Naess (1973), the first published work inenvironmental ethics and began a central debate in the area, oneconcerned with intrinsic value in nature. Elaborated on in Routley andRoutley (1979b) and (1980a), this work developed arguments againstwhat he termed “human chauvinism”—the view thathumans are exceptional in being the sole locus of intrinsic value, allelse having merely instrumental value. Alongside this work inenvironmental ethics more broadly, which was to continue until hisdeath, he also published in defence of pacifism, against nuclear war,and was one of the first philosophers to point to the emerging moralissues associated with anthropogenic global warming.

4.1 The Last Man Example

Developing out of influential work condemning Australian forestrypractices in the early 1970s, (cf. Routley and Routley 1973a, Byron1999), Routley (1973)—“Is There a Need for a New, anEnvironmental, Ethic?”—presents a thought experimentdesigned to test what Sylvan took to be a core principle of Westernethical systems, the Freedom Principle:

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

He calls this principlebasic human chauvinism “becauseunder it humans, or people [whether present or future], come first andeverything else a bad last”—a view later characterized as“anthropocentric” in the much expanded discussion of TheLast Man Example in Routley and Routley (1980a, cf. 96).

We are invited to consider a world in collapse where humanity isreduced to a single person who then proceeds to eliminate, to the bestof their abilities, “every living thing, animal or plant (butpainlessly if you like, as at the best abattoirs).” (1973, 16)With the demise of the last man (which we may suppose occursimmediately prior to the wholesale destruction unleashed), there areno humans—either others or the last man himself—who couldbe 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” wereextended 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 andassociated Western ethical systems, and a claimed need for a newethic, “an environmental ethic”, capable of accounting forthe wrongness of the last man’s act. (As in his logical work,Sylvan’s strategy is to try to isolate what is sufficient (inthis case, for wrongness) by considering “distant”possible worlds.)

Granting the wrongness of the last man’s act, is a “newethic” really required? Preference utilitarianism has beenconsidered as a “traditional” ethic capable of condemningthe last man. (Cf. Elliot 1980, 20 and 23; and Carter 2004,51–52 for a more limited condemnation along preferenceutilitarian grounds.) Where there is an overwhelming preference forpreservation of the world beyond the death of the last man, and itsdestruction would thus harm those having such a preference, theFreedom Principle would already appear to prohibit such an act(assuming the aggregated harm outweighs any benefit in thesatisfaction of contrary preferences). But notice that condemnation,on this view, is highly contingent, depending on people’spreferences (condemnation is justifiedonly if preferencesconflict with destruction). Since the condemnation is thought to bewarranted with “no ifs and buts”, yet this“traditional” response offers the correct judgement onlyin special circumstances, for Sylvan, it counts as “tooparochial” (Routley 1973, 20). (Cf. Lamb 2018, 532–3 for asimilar point.)

Reacting, in part, to Leopold’s call for a “landethic”, Sylvan’s subsequent work in the area (much of theearly work with Val Routley, later Val Plumwood) proceeds to describeand argue for just such a non-anthropocentric, environmental ethic. Adominant aspect of this “new” ethic (indeed, acharacterising feature in Elliot 1980) that was fixed on bysubsequent authors was the extension of non-instrumental,“intrinsic” or “final” values to the non-humanworld. First mentioned in 1974 in early drafts of Routley and Routley(1980a) and subsequently Val Routley (1975), Rolston (1975), andCallicott (1979)—who all employ versions of the Last ManExample—the extension is described and defended at length inRoutley and Routley (1980a). (Sylvan assumes intrinsic value is, ingeneral, already assured on the familiar Aristotelian ground thatinstrumental value requires intrinsic value, lest vicious regressensue—cf. AristotleMetaphysics, 994b9–15.)

Sylvan and Plumwood hypothesise that what underpins the deonticprohibition of the last man’s act is the truth of theaxiological claim that entities in non-human nature can possess morethan mere instrumental value—non-human nature “can havevalue and create obligations not reducible (in any way) to humaninterests” (1980a, 129). While such items may have instrumentalvalue, value as a means to human ends, advantaging us in variousways—e.g., the value of forests in supplying water for humanconsumption—they might also have “non-instrumental”,or what the Routleys called “intrinsic” value (1980a, 126and 129). Thus, the rejection of human chauvinism in its deontologicalform (the assertion of and the argument to the falsity of the FreedomPrinciple) was accompanied by its rejection in axiological form: notonly humans have intrinsic value; non-human nature may also be thelocus of intrinsic (non-instrumental) value.

While accepting that we may have moral obligations with respect to orregarding entities in the non-human world, Routley (1973, 19) andRoutley and Routley (1980a, 174ff) deny that this entails our havingobligationsto them and deny, too, their having correlativerights. Sylvan rejects such an extension of rights to non-humanentities. For this reason, he takes the “new environmentalethic” to “differ markedly” from alternatives likeLeopold’s land ethic. As it developed, it also differed markedlyfrom most forms of utilitarianism for a broad range of reasons,arguing instead for a deontologically constrained “optimisationapproach to value theory”. (See Routley and Routley 1985; Sylvan1992.) Variants of Last Man counterexamples to traditional Westernethics are also taken to show that the distribution of intrinsic valueextends beyond sentient individuals—contra “animalliberationists” (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 inevitabilityof human chauvinism. Foremost among them are arguments that, heclaims, “parallel” arguments for egoism. Their rejectionfollows similar grounds for rejection of egoism—cf. Routley andRoutley (1979b, esp. 47). This paper also distinguishes strong formsof human chauvinism (endorsing what Sylvan later termed the sole valueassumption: thatonly members of the human class and some oftheir possible states have intrinsic value) from weaker forms thatmerely endorse, for example, “the Greater Value Thesis: theinvariable allocation of greater value or preference … tohumans, while not however entirely excluding non-humans from moralconsideration” (ibid., 36)—a thesis also rejectedby Sylvan. Paske (1991) defends a qualified version of the thesis; themoral differentiation in favour ofmost humans can bejustified (by appeal to deontologically-constrained hedonicconsequentialism). Attfield (1981), considering versions of the LastMan Example, also rejects strong human chauvinism while defending thegreater value thesis, thus defending a weak chauvinism inSylvan’s sense. “The good of trees might outweigh some ofour whims: but it does not outweigh our interests except where ourinterests depend on it” (1981, 51).

Petersen and Sandin, on the other hand, defend a strong form of humanchauvinism, arguing that the Last Man Example is subject to varyingresponses depending on themotives attending the act ofelimination. They thus reject the hypothesis of intrinsic values innature, arguing instead that any supposed wrongness “can bebetter explained by precepts about last man’s character traitsand motives” (2013, 133). It remains open whether such aresponse is adequate for the Last People Example (described by Sylvanimmediately 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 intrinsicvalue of natural items focus on supposed problems that attend theapparently “cosmic” account of value that items are saidto have in the absence of valuers (e.g., after the demise of the lastman). Some focus on problems traditionally associated with moralobjectivism. 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 inconsistentwith (the preferred theory) moral projectivism (Carter 2004, whoclaims a projectivist theory can explain our intuitions concerning thelast man); or such value is simply beyond epistemic access andirrelevant for decision-making (Justuset al. 2009,187–8). The latter point echoes earlier claims in Thompson(1990), Grey (1993), and Fox (1995) that the hypothesis of intrinsicvalue in nature results in values that, being too far removed fromhuman concerns, are irrelevant as an ethical guide to human action(Thompson 1990, 159–60; Grey 1993, 464) and, in any event, areunnecessary—an enlightened anthropocentrism is sufficient.

Sylvan’s position on the ontology of values (discussed at lengthin 1980a, esp. 152ff) draws on the Last Man Example to claim thatthings can, indeed, be valuable at a time when no valuers exist andextended thought experiments of a similar kind he takes to furtherestablish that things can be valuable in a world wherein no valuerexists 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 “novalue without valuers” remains true, he contends—andtherewith the rock of objectivism is said to be avoided (1980a, 154).Elliot (1980) also contends that a non-objectivist account issufficient for this kind of value engendered by the last man example,though it is one requiringactual evaluators (“novalues without actual valuers”). He goes on to describe asubjectivist account that further links values to valuers ina manner that “makes the valuer the sole determinant of athing’s value” (1980, 19) with value reduced to valuerevaluations.

Taking himself to have avoided objectivism, Sylvan nonetheless arguesagainst subjectivist accounts—intrinsic values are notsubjective either (1980a, 154). Intrinsic valuein a world,while depending conceptually on valuers, nonetheless does not reduceto valuersin that world in any way. Some have remarked onthe apparent similarities between Sylvan’s account of intrinsicvalue and secondary qualities, suggesting his account amounted to aresponse-dependent account of intrinsic value (cf. Grey 2000). SeeLamb (2018, §IX) for argument to the contrary.

In the further elaboration of the “new ethic”, Routley andRoutley (1980a) develops a multiple factor model combining traditionalvalues, such as the virtues and creature enjoyment, with environmentalvalue-making factors, for example: diversity of systems and creatures,naturalness, integrity of systems, stability of systems, and harmonyof systems (170–171). So the shift to an environmental ethicdoes not reject ordinarily acknowledged welfare values for persons orhumans, but simply recognises a further set of factors contributing tointrinsic value in nature (171). Such value-making factors enter intoa mutually constrained optimisation so that the increase of one neednot increase the overall intrinsic value of the entity exemplifyingit; thus, an increase in diversity in a forest may decrease valueinsofar as it may come at the cost of naturalness (e.g., if the addeddiversity comes from the anthropogenic addition of feral species notnaturally occurring in that forest).

The account of value is non-naturalistic in the sense that value isargued to be irreducible to natural features, even though“grounded” in them. (1980a, §5; Sylvan latercommitted to the supervenience of intrinsic value on naturalisticfeatures, Sylvan and Bennett 1994, 143). It is Meinongian in a numberof respects—most obviously, drawing freely on Routley (1980),cf. esp. §8.11, values are features had by items but, likeproperties, they do not exist (1980a, 153ff). Sylvan’s moralepistemology also draws heavily on Meinong’s account of“emotional presentation” (see Lamb 2018, §VIII):“the valued object may be emotionally presented and its valuethus recognised, without its value simply amounting to itsemotional presentation” (Routley and Routley 1983, 453). Theaccount is articulated at length in Sylvan (1986). Perhapsunsurprisingly, Sylvan’s semantic analysis of value (cf. Routleyand Routley 1983) makes use of non-classical, relevant logic in itsformal analysis. (Weber 2017a also draws on Sylvan’s work innon-classical logic to develop a “new version” of the LastMan Example—the “Ultramodal Last Man”—with aview to avoiding an alleged dilemma besetting the original Last ManExample, “renewing a role for non-standard logics in valuetheory”.)

4.2 Deep Green Ethics

While Sylvan views the development of deep ecology sympathetically, hedistances himself from the positions being argued for under thatbanner. His own “deep green ethics” is described mostclearly in Sylvan and Bennett (1994, ch. 5). Like deep ecology, theposition is, using the term originally coined in Naess (1973),“deep” since it rejects the sole value assumption andgreater value thesis. But unlike deep ecology Sylvan rejects, inparticular:

biocentrism—“all and only life is valuable”

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

biospherical egalitarianism—“the equal value of alllife”

arguing instead for eco-impartiality, thus not valuing members of onespecies over those of another simply on the basis of speciesmembership, and noting that evaluative impartiality with respect tospecies does not entail their equal value. More generally, Sylvan(1985) argues that under the strong West Coast US influence deepecology commits to an assortment of dubious metaphysical andpsychological themes—often leading to an anthropocentric“person- and consciousness-oriented soufflé”. Andlinks 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 thesepoints of difference with deep ecologists in uncompromising styleearned him the title ‘the bad boy of deep ecology’ (Orton2005, Other Internet Resources). For responses, see Fox (1986) andAttfield (1993).

His deep green theory is, following his metaphysical and logicalpluralism (cf. Sylvan 1997), also pluralistic “allow[ing] forthe requisite theory dependence and cultural relativity ofvalues” (1980a, 156), “there is no uniquely determinedcorrect value system … there are various overlappingsystems” though he denies that ethical relativism follows fromthis (Sylvan 1986, 13). He sees the ongoing cultural project ofdeveloping an adequate environmental ethic as being in its earlystages.

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

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

Consider an area of restored bushland … The restoration resultsprimarily by nature doing its own thing; it is nothing like furnitureor pottery making. An ecological restorer, unlike an artisan, does notproduce the item, there is no making … Rather there isadjustment at margins … and there ishelping inhealing (Sylvan 1994, 68).

Sylvan argues that Elliot and Katz have illicitly extended the notionof an artifact, which is widely and wrongfully deployed in suchdescriptions of restored natural areas and what they (especially Katz)have failed to grasp is the value-enhancing role that restorationplays in the many situations where the damage has already been done.Such restoration “is an addition, an attempt … to claimback much more of what has [already] been grabbed and degraded orruined” (Ibid., 75). In many cases restoration assistsnature in reasserting itself and taking control once more. Whatresults lacks certain properties of the original, to be sure,especially natural continuity, but contributing to the restoration ofsomething to close-to-original value (as opposed to some low-valuefake) is, Sylvan argues, worthwhile and can result in near-naturalareas of enormous value. That is value enough.

Though Sylvan is uneasy using the term ‘wilderness’“due to its long history of unfavourable associations andconnotation”, he agrees with the broader point being made byElliot and Katz—“ecological restoration isnot analternative to retaining wilderness, to remnant wildernesses”(Sylvan 1994, 75). However, they have overstated their case concerningthe value of restored landscapes. Elliot was persuaded, admitting thathe paid too little attention to the types of restoration that can beachieved and underestimated the value and degree of naturalness thatcan result. In a book-length response to Sylvan and other critics andfellow travellers, Elliot (1997) clarifies his argument. Its Prefaceacknowledged the enormous debt to Sylvan. He is, Elliot came to think,quite right. “Mucking with nature” can result in somethingof significant value and it is, Elliot argued, in many casesobligatory to try to undo the damage we have done.

A further practical issue which Sylvan sees as requiring theoreticaljustification is predation: the killing of animals for food.“The vegetarian options face, it certainly seems, insuperabledifficulties, especially concerning such issues as animal predation(which is an important, immensely frequent, and oftendesirable, ecological fact), and concerning the reduction innumbers of animals, especially introduced animals, which build up to‘pest proportions’ (some reduction is often required forvegetable 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 intrinsicallyvaluable non-humans, he argues that the

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

See Routley (1982, §4) for a defence (a paper which also presentsa moral defence of limited cannibalism). For a similar view seeCallicott (1980) and for defence of the contrary claim that we ought,where possible, act to eliminate predation, even cases of wild animalstaking prey for food, see Nussbaum (2007, ch. 6).

4.3 Further Moral Theory

In addition to work in environmental ethics, Sylvan wrote on otherethical issues including arguments for moral obligations to futuregenerations (cf. Routley and Routley 1978, Sylvan and Plumwood 1991),and the ethics of energy choice (Routley and Routley 1979c). Theargument offered in the latter paper against nuclear power centres onthe (anthropocentric but nonetheless, in Sylvan’s view, salient)claim that bequeathing toxic nuclear waste to future generationsconstitutes an ethically unacceptable shift of costs onto others. Anda similar argument was mounted against conspicuous consumption offossil fuels from what Sylvan and Plumwood then referred to as“atmosphere heating” (Routley and Routley 1979c, §3).Theirs appear to be amongst the earliest philosophical discussionsfocussing on the ethics of climate change. And it is not just theclaimed immorality following from the consequences of climate changeto future humans, though that is given weight; from a deep greenperspective, the claimed erosion of value outstrips mereanthropocentric concerns and needs to take into account non-humannature, where the resultant erosion of intrinsic value is taken toloom large.

Considering destructive practices more generally, beyond thosedestructive of the environment, Sylvan considered violence againstpersons, arguing that not only was nuclear war immoral, but that whichconditionally 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 inRoutley (1984b).

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

(PC): $\mathrm{O}A \rightarrow \twiddle\mathrm{O}\twiddleA$

and the Kantian principle ought-implies-can (since dilemmas createimpossible obligations). He argues that the sentential fragment ofdeontic logic must be paraconsistent and a relevant logic isrecommended (see Section 2).

Sylvan saw his ethics as systematically connected with issues insocial and political philosophy, extending out from “deep greenethics” to a broader “deep green theory” that“includes a radical social and political theory, centred uponsocial anarchistic forms of organization … and elements ofradical economic theory … Therehave to be changes insocial and political arrangements … towards less consumptive,populous and wasteful societies, and so on” (Sylvan and Bennett1994, 151).

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

4.4 Summary

Sylvan’s work in moral theory helped pioneer the rise ofenvironmental philosophy as a new sub-discipline and connectedenvironmental issues with broader moral issues as well as issues inpolitical and social philosophy. Drawing on other work in metaphysicsand logic, he sought new non-anthropocentric moral foundations,heavily critical of both traditional ethics and emerging alternativesthat lacked clarity and rigour.

5. Conclusion

The overall picture that emerges from Sylvan’s work is of abroad philosophy that draws on non-classical (relevant) logic, aneo-Meinongian metaphysics and a neo-Meinongian value theory as ameans of accounting for “common-sense” ways of talking(e.g., about things that do not exist), ways of valuing (e.g., theseeming intrinsic value of things in the natural world) andsocio-political arrangements (e.g., a pluralist anarchism).Sylvan’s work was radical, but rigorous; a rich many-worldssemantics underpins formal analyses. His work was contentious; manytraditional philosophical “problems” are claimed to beartefacts of faulty orthodox theories. And his work was expansive;philosophy’s traditional role with the question “How arewe to live?” is taken seriously. Above all, Sylvan’sthought was unified and systematic: “What is sought is a theoryof values which blends both with object-theory and with deeperenvironmental theory…” (1986, 1).

Sylvan’s program was left unfinished when he died. Whatever onethinks of his bold statements (“a wild mixture of wonderfullyincisive ideas and absolutely false claims,” as Meyer put it in1996), Sylvan pushes philosophers to recognize that many propositionstaken as facts are not unrestrictedly true, but rather arerelative to what assumptions one is making about logic,ontology, and value. Changing those assumptions changes thepossibilities. And Sylvan’s work urges us to be ready for morepossibilities—even what is, as he put it, “beyond thepossible” (this is the title of an unpublished manuscript citedin Routley 1980).

Bibliography

Primary Literature

Brady, R. and Routley, R., 1973, “Don’t Care was Made toCare”,Australasian Journal of Philosophy, 51:211–225.
Brady, R. (ed.), 2003,Relevant Logics and their Rivals II: Acontinuation of the work of Richard Sylvan, Robert Meyer, Val Plumwoodand Ross Brady, Ashgate: Aldershot.
Copeland, B.J. and Sylvan, R., 1999, “Beyond the UniversalTuring Machine”,Australasian Journal of Philosophy,77: 46–66.
Eckert, M. (ed.), 2018,Exploring Meinong’s Jungle andBeyond, (The Sylvan Jungle: Volume 1), with Introductionby Dominic Hyde, Cham: Springer.
Goddard, L. and Routley, R., 1973,The Logic of Significanceand Context (Volume 1), Edinburgh and London: Scottish AcademicPress.
Hyde, D. (ed.), 2019,Noneist Explorations I (TheSylvan Jungle: Volume 2), Cham: Springer.
–––, 2020,Noneist Explorations II(The Sylvan Jungle: Volume 3), Cham: Springer.
Hyde, D. and Sylvan, R., 1993, “Ubiquitous Vagueness withoutEmbarrassment”,Acta Analytica, 10: 7–29.
Meyer, R. K. and Routley, R., 1977, “Extensional Reduction(I)”,The Monist 60: 355–369.
Nozick, R. and Routley, R., 1962, “Escaping the GoodSamaritan Paradox”,Mind, 71: 377–386.
Priest, G., and Routley, R., 1983,On Paraconsistency,Research Report #13, Research School of Social Sciences, AustralianNational University,1984 reprint available online; reprinted in Priest, Routley, and Norman (eds.) 1989.
Routley, R., 1965, “What Numbers Are”,Logique etAnalyse, 8: 196–208.
–––, 1966a, “Some Things Do NotExist”,Notre Dame Journal of Formal Logic, 7:251–76.
–––, 1966b, “On A SignificanceTheory”,Australasian Journal of Philosophy, 44:172–209.
–––, 1969, “The Need for Nonsense”,Australasian Journal of Philosophy, 47: 367–384.
–––, 1973, “Is There a Need For a New, anEnvironmental, Ethic?”,Proceedings of the XVth WorldCongress of Philosophy, Varna, 1: 205–10; reprinted in M.Zimmermanet al. (eds.),Environmental Philosophy: fromAnimal Rights to Radical Ecology, Englewood, NJ: Prentice Hall:1993, p.12–21; page references are to this reprint.
–––, 1975, “Universal Semantics?”,Journal of Philosophical Logic, 4: 327–56.
–––, 1977, “Ultralogic asUniversal?”,Relevance Logic Newsletter, 2: 50–90and 138–75; reprinted in Routley 1980, Appendix; also reprintedin Weber (ed.) 2019, pp. 1–121; page references are to thereprint in Routley 1980.
–––, 1979a, “The Semantical Structure ofFictional Discourse”,Poetics, 8: 3–30.
–––, 1979b, “Dialectical Logic, Semanticsand Metamathematics”,Erkenntnis, 14: 301–331.
–––, 1980,Exploring Meinong’s Jungleand Beyond: An investigation of noneism and the theory of items,Department of Philosophy Monograph Series #3, Canberra: AustralianNational University; reprinted in Eckert (ed.) 2018, pp.xxxv–507.
–––, 1980a, “The Choice of LogicalFoundations: Non-classical choices and the ultralogical choice”,Studia Logica, 39(1): 77–98.
–––, 1982, “In Defence of Cannibalism I:Types of admissible and inadmissible cannibalism”, DiscussionPapers in Environmental Philosophy #2, Canberra: Australian NationalUniversity.
–––, 1983, “Nihilism and NihilistLogics”, Discussion Papers in Environmental Philosophy #4,Canberra: Australian National University.
–––, 1984a, “On the Ethics of Large-ScaleNuclear War and Nuclear Deterrence and the Political Fall-Out”,Discussion Papers in Environmental Philosophy #5, Canberra: AustralianNational University.
–––, 1984b, “On the Alleged Inconsistency,Moral Insensitivity and Fanaticism of Pacifism”,Inquiry, 27: 117–148.
–––, 1984c, “Research in Logic inAustralia, New Zealand and Oceania: Its brief history and its presentstate”,Ruch Filozoficzny, 41: 127–162; reprintedfrom Research Papers in Logic #14, Research School of Social Sciences,Canberra: Australian National University, 1983.
Routley, R. and Meyer, R.K., 1976, “Dialectical Logic,Classical Logic and the Consistency of the World”,Studiesin Soviet Thought, 16: 1–25.
Routley, R., Meyer, R.K., Plumwood V. and Brady, R., 1982,Relevant Logics and Their Rivals I. The basic semanticaltheory, Atascadero: Ridgeview.
Routley, R. and Plumwood, V., 1986, “The ‘Fight forthe Forests’ affair” in B. Martinet al. (eds.),Intellectual Suppression, Sydney: Angus and Robertson, pp.70–3.
Routley, R. and V., 1972, “The Semantics of First DegreeEntailment”,Noûs, 6: 335–58.
–––, 1973a,The Fight for the Forests: theTakeover of Australian Forests for Pines, Wood Chips and IntensiveForestry, Research School of Social Sciences, Canberra:Australian National University.
–––, 1973b, “RehabilitatingMeinong’s Theory of Objects”,Revue Internationale dePhilosophie, 27: 224–54.
–––, 1978, “Nuclear Energy and Obligationsto the Future”,Inquiry, 21: 133–79; reprintedin: E. Partridge (ed.),Responsibilities to Future Generations:Environmental Ethics, Buffalo: Prometheus Books, 1981, pp.277–301.)
–––, 1979a, “The (Logical) Importance ofNot Existing”,Dialogue, 18: 129–65.
–––, 1979b, “Against the Inevitability ofHuman Chauvinism” in K.E. Goodpaster and K.M. Sayre (eds.),Ethics and the Problems of the 21st Century, South Bend:Notre Dame University Press.
–––, 1979c, “Some Ethical Aspects ofEnergy Choice” in M. Diesendorf, R. Bartell, C. Casey, A. Day,L.H. Day, R.M. Gifford and H. Saddler (eds.),Energy and People:Social Implications of Different Energy Futures, Canberra:Society for Social Responsibility in Science (A.C.T.), pp.113–116.
–––, 1980a, “Human Chauvinism andEnvironmental Ethics” in D. Mannison, M. McRobbie and R. Routley(eds.),Environmental Philosophy, Department of PhilosophyMonograph Series #2, Canberra: Australian National University, pp.96–189.
–––, 1982, “Nuclear Power — Ethicaland Social Dimensions” in D. Van der Veer and T. Regan (eds.),And Justice For All, Totowa, NJ: Rowman and Littlefield, pp.116–138.
–––, 1983, “The Semantic Foundations forValue Theory”,Noûs, 17: 441–456.
–––, 1985, “An Expensive Repair-Kit forUtilitarianism”, Discussion Papers in Environmental Philosophy#7, Canberra: Australian National University, pp. 21–55.
Routley, V. and Routley, R., 1980b, “Social Theories, SelfManagement and Environmental Problems” in D. Mannison, M.McRobbie and R. Routley (eds.),Environmental Philosophy,Department of Philosophy Monograph Series #2, Canberra: AustralianNational University, pp. 217–332.
Sylvan, R., RSC,Richard Sylvan Collection, FryerLibrary, University of Queensland.
–––, 1985, “A Critique of DeepEcology”, Discussion Papers in Environmental Philosophy #12,Canberra: Australian National University; reprinted in serialisedform: “A Critique of Deep Ecology, Part I”,RadicalPhilosophy, 40 (1985): 2–12; “A Critique of DeepEcology, Part II”,Radical Philosophy 41 (1985):10–22. Reprinted in M. Redclift and G. Woodgate (eds.),TheSociology of the Environment, London: Edward Elgar, 1995.
–––, 1986, “The Way of Values: A freevariation of Meinong’s theory of impersonal value” in R.Sylvan,Three Essayes Upon Deeper Environmental Ethics,Discussion Papers in Environmental Philosophy #13, Canberra:Australian National University, pp. 1–27; reprinted in P. Simons(ed.)Essays on Meinong, Munich: Philosophia Verlag,1992.
–––, 1991, “Sistology” in L.Burkhardt and B. Smith (eds.),The Handbook of Metaphysics andOntology, Munich: Philosophia Verlag, pp. 837–840.
–––, 1992, “On the Value Core of DeepGreen Theory” in G. Oddie and R. Perrett (eds.),Justice,Ethics and New Zealand Society, Auckland: Oxford UniversityPress, 1992, pp. 222–229.
–––, 1994, “Mucking With Nature” inAgainst the Main Stream: Critical Environmental Essayes,Discussion Papers in Environmental Philosophy #20, Canberra:Australian National University.
–––, 1995a, “Re-Exploring ItemTheory”,Grazer Philosophische Studien, 50:47–85.
–––, 1995b, “Item Theory Made Easy”,unpublished typescript, Sylvan Papers, folder #1234, Fryer Library,University of Queensland.
–––, 1997,Transcendental Metaphysics,Winwick: White Horse Press. (Reprinted 2022.)
–––, 2000a,Sociative Logics and theirApplications: Essays by the late Richard Sylvan, D. Hyde and G.Priest (eds.), Aldershot: Ashgate.
Sylvan, R. and Bennett, D., 1994,The Greening of Ethics: FromHuman Chauvinism to Deep-Green Theory, Winwick: White HorsePress, and Tuscon: The University of Arizona Press.
Sylvan, R. and Copeland, J., 2000, “Computability is LogicRelative” in Sylvan 2000a, pp. 189–199.
Sylvan, R. and Nola, R., 1991, “Confirmation WithoutParadoxes” in G. Schurz and G. Dorn (eds.),Advances inScientific Philosophy, Leiden: Brill, pp. 5–44.
Sylvan, R. and Plumwood, V., 1991, “FutureGenerations” in A. Dobson (ed.),The Green Reader,London: André Deutsch, pp. 250–252.
Weber, Z. (ed.), 2019,Ultralogic as Universal? (TheSylvan Jungle: Volume 4), Cham: Springer.

Secondary Literature

Albertazzi, L., 2013, “Dissecting Intentionality in the Lab:Meinong’s Theory”,Axiomathes, 23:579–596.
Anderson, A.R. and Belnap, N.D., 1975,Entailment: The Logicof Relevance and Necessity (Volume 1), Princeton: PrincetonUniversity Press: Princeton.
Attfield, R., 1981, “The Good of Trees”,Journalof Value Inquiry, 15: 35–54.
–––, 1993, “Sylvan, Fox and Deep Ecology:A View From the Continental Shelf”,EnvironmentalValues, 2: 21–32.
Barz, W., 2014, “Doubts about One Own’sExistence”,Inquiry, 57: 645–668.
Beall, J.C., 2009,Spandrels of Truth, Oxford: OxfordUniversity Press
Beall, J. and Restall, G., 2000, “Logical pluralism”,Australasian Journal of Philosophy, 78: 475–493.
Beall, J., Brady, R., Dunn, J.M., Hazen, A.P., Mares, E., Meyer,R.K., Priest, G., Restall, G., Ripley, D., Slaney, J., and Sylvan, R.,2012, “On the Ternary Relation and Conditionality”,Journal of Philosophical Logic, 41: 595–612.
Berto, F., 2013,Existence as a Real Property, Dordrecht:Springer.
–––, 2015, “A Modality Called‘Negation’”,Mind, 124(495):761–793.
Berto, F. and Jago, M., 2019,Impossible Worlds, Oxford:Oxford University Press.
Berto, F. and Restall, G., 2019, “Negation on the AustralianPlan”,Journal of Philosophical Logic, 48(6):1119–1144.
Besoli, S., 1984, “Convergences and Diversities BetweenNoneism and Gegenstandstheorie”,Grazer PhilosophischeStudien, 21: 133–153.
Bourgeois, V.W., 1981, “Beyond Russell and Meinong”,Canadian Journal of Philosophy, 11: 653–666.
Bradley, M., 1978, “On the Alleged Need For Nonsense”,Australasian Journal of Philosophy, 56: 203–218.
Brady, R.T., 1971, “The Consistency of the Axioms ofAbstraction and Extensionality in a Three-Valued Logic”,Notre Dame Journal of Formal Logic, 12(4):447–453.
–––, 1980, “Two Remarks on the Logic ofSignificance and Context”,Notre Dame Journal of FormalLogic, 21: 263–272.
–––, 1989, “The Non-Triviality ofDialectical Set Theory”, in G. Priest, R. Routley and J. Norman(eds.),Paraconsistent Logic, Munich: Philosophia Verlag, pp.437–470.
–––, 2006,Universal Logic, Stanford:CSLI Publications.
Brady, R.T. and Mortensen, C., 2014, “Logic”, in OppyG., Trakakis N. (eds.)History of Philosophy in Australia and NewZealand, Dordrecht: Springer.
Bunder, M.W., 1979, “Deduction Theorems in SignificanceLogics”,Notre Dame Journal of Formal Logic, 20:695–700.
–––, 1980a, “A Note on QuantifiedSignificance Logic”,Bulletin of the Section of Logic,9: 159–162.
–––, 1980b, “Significance and IllativeCombinatory Logics”,Notre Dame Journal of FormalLogic, 21: 380–384.
Burgess, J.P., 1983, “Common Sense and‘Relevance’”,Notre Dame Journal of FormalLogic, 24(1): 41–44.
Byron, N., 1999, “Forestry As If Economics Mattered”in G. Borschmann,The People’s Forest: A Living History of theAustralian Bush, Canberra: People’s Forest Press, pp.49–59.
Callicott, J.B., 1979, “Elements of an Environmental Ethic:Moral Considerability and the Biotic Community”,Environmental Ethics, 1: 71–81.
–––, 1980, “Animal Liberation: ATriangular Affair”,Environmental Ethics, 4:311–38.
Campbell, R., 1972, “Did Meinong Plan a Jungle?”,Philosophical Papers, 1: 89–102.
Carter, A., 2004, “Projectivism and the Last Person”,American Philosophical Quarterly, 41(1): 51–62.
Casati, F., 2015, “Profili: Richard Routley Sylvan”,APhEx: Giornale di Filosofia, Number 12 (06 July 2015),Casati 2015 available online.
–––, 2018, “The Future Perfect ofExploring Meinong’s Jungle and Beyond”, in Eckert(ed.) 2018, pp. 583–601.
Casati, F. and Fujikawa, N., 2019, “Nothingness,Meinongianism and Inconsistent Mereology”,Synthese,96(9): 3739–3772.
Casati, F., Mortensen, C. and Priest, G., 2018,The Philosophyof Richard Sylvan, special issue of theAustralasian Journalof Logic, 15(2).
Casati, F. and Priest, G., 2017, “InsideAussersein”,IFCoLog Journal of Logics and theirApplications, 4: 1–14.
Chomsky, N., 2013,On Anarchism, New York: The NewPress.
Cocchiarella, N.,, 1984, “Review of ‘The Logic ofSignificance and Context”,Journal of Symbolic Logic,49(4): 1413–1414.
Copeland, B.J., 1979, “On When a Semantics is not aSemantics: Some Reasons For Disliking The Routley-Meyer Semantics ForRelevance Logic”,Journal of Philosophical Logic, 8:399–413.
–––, 1983, “A Rejoinder To Routley,Routley, Meyer and Martin”,Journal of Non-ClassicalLogic, 2: 61–66.
Crane, T., 2012, “What is The Problem ofNon-Existence?”,Philosophia, 40: 417–434.
–––, 2013,The Objects of Thought,Oxford: Oxford University Press.
De, M. and Omori, H., 2018, “There is More to Negation ThanModality”,Journal of Philosophical Logic, 47(2):281–299.
Elliot, R., 1980, “Why Preserve Species?”, in D.Mannison, M. McRobbie, and R. Routley (eds.),EnvironmentalPhilosophy, Monograph Series #2, Canberra: Australian NationalUniversity, pp. 8–29.
–––, 1982, “Faking Nature”,Inquiry, 25: 81–93.
–––, 1997,Faking Nature: the Ethics ofEnvironmental Restoration, London: Routledge.
Ficara, E., 2021, “The Birth of Dialetheism”,History and Philosophy of Logic, 42(3): 281–296.
–––, 2023, “Review of R. Routley, Ultralogic asUniversal, Sylvan Jungle volume 4”,History and Philosophyof Logic, online November 2023.
Field, H., 2008,Saving Truth from Paradox, Oxford:Oxford University Press.
Fine, K., 1982, “The Problem of Non-Existents”,Topos, 1: 97–140.
–––, 1974, “Models for Entailment”,Journalof Philosophical Logic, 3: 347–372.
Fitelson, B., 2006, “The Paradox of Confirmation”,Philosophy Compass, 1(1): 95–113.
Fox, W., 1986, “Approaching Deep Ecology: A Response ToRichard Sylvan’s Critique Of Deep Ecology, EnvironmentalStudies”, Occasional Paper 20, Centre for Environmental Studies,Hobart: University of Tasmania.
–––, 1993, “What Does the Recognition ofIntrinsic Value Entail?”,Trumpeter, 10: 101.
–––, 1995,Toward a Transpersonal Ecology:Developing New Foundations for Environmentalism, Albany: StateUniversity of New York Press.
Fuhrmann, A., 1990, “Models for Relevant ModalLogics”,Studia Logica, 49: 501–514.
Goddard, L., 1970, “Nonsignificance”,AustralasianJournal of Philosophy, 48: 10–16.
–––, 1977, “The Paradoxes of Confirmationand the Nature of Natural Laws”,PhilosophicalQuarterly, 27(107).
–––, 1992, “A Personal View of theDevelopment of Deductive Logic in Australia since 1956”, in J.Srzednicki and D. Wood (eds.),Essays on Philosophy inAustralia, Dordrecht: Kluwer, pp. 169–185.
–––, 1996, speech to Memorial gathering uponSylvan’s death, Canberra: Australian National University.
Goodman, N., 1978,Ways of Worldmaking, Indianapolis, IN: Hackett Publishing Company.
Grey, W., 1993, “Anthropocentrism and Deep Ecology”,Australasian Journal of Philosophy, 71: 463–475.
–––, 2000, “A Critique of DeepEcology”, in Katz,et al. (eds.),Beneath theSurface, Cambridge, MA: MIT Press, pp. 43–58.
–––, 2008a, “Last Man Arguments”, inJ.B. Callicott and R. Frodeman (eds.),The Encyclopedia ofEnvironmental Ethics and Philosophy (Volume 2), New York:Macmillan, pp. 40–41.
–––, 2008b, “Sylvan, Richard”, inJ.B. Callicott and R. Frodeman (eds.),The Encyclopedia ofEnvironmental Ethics and Philosophy (Volume 2), New York:Macmillan, pp. 298–9.
Griffin, N., 1982, “Meinong’s Jungle andRussell’s Desert”,The Journal of Bertrand RussellStudies, 2: 53–60.
–––, 2018, “Why Item Theory Doesn’t(Quite) Go Far Enough”, in Eckert (ed.) 2018, pp.509–545.
Grossman, R., 1974,Meinong. The Arguments ofPhilosophers, New York: Routledge.
–––, 1984, “Nonexistent Objects VersusDefinite Descriptions”,Australasian Journal ofPhilosophy, 62: 363–377.
Grzankowski, A., 2013, “Non-propositional Attitude”,Philosophy Compass, 8: 1123–1137.
–––, 2016, “Attitudes TowardsObjects”,Noûs, 50(2): 314–328.
Haack, R.J., 1971, “No Need For Nonsense”,Australasian Journal of Philosophy, 49: 71–77.
–––, 1975, “Still No Need ForNonsense”,Australasian Journal of Philosophy, 53:161–164.
Havas, K.G., 1981, “Some Remarks on an Attempt atFormalizing Dialectical Logic”,Studies in SovietThought, 22: 257–265.
Hyde, D., 2000, “Richard (Routley) Sylvan: Writings on Logicand Metaphysics”,History and Philosophy of Logic, 22:181–205.
–––, 2014,Eco-Logical Lives: thephilosophical lives of Richard Routley/Sylvan and ValRoutley/Plumwood, Winwick: The White Horse Press.
–––, 2018, “Is There a Need for IntrinsicValues in Conservation Biology?”,Australasian Journal ofLogic, 15: 498–512.
–––, 2021, “Sylvan, Richard(1935–1996)”,Australian Dictionary of Biography,National Centre of Biography, Australian National University,available online.
Jacquette, D., 1996, “On Defoliating Meinong’sJungle”,Axiomathes, 7: 17–42.
–––, 2013, “About Nothing”,Humana Mente, 25: 95–118.
–––, 2015,Alexius Meaning: the Shepherd ofNon-Being, New York: Springer.
–––, 2017, “Nuclear and ExtranuclearProperties”, in L. Albertazzi and D. Jacquette,The Schoolof Alexius Meinong, New York: Routledge.
Jorgensen, A.K., 2004, “Types of Negation in LogicalReconstructions of Meinong”,Grazer PhilosophischeStudien, 67: 21–36.
–––, 2013, “Meinong on Intending”,International Journal of Philosophical Studies, 21:415–427.
Justus, J., Colyvan, M., Regan, H. and Macquire, L. (2009),“Buying in to Conservation: Intrinsic versus instrumentalvalue”,Trends in Ecology and Evolution, 24:187–191.
Katz, E., 1992, “The Big Lie: Human Restoration ofNature”,Research in Philosophy and Technology, 12:231–41.
Kielkopf, C.F., 1974, “Critique of the Routleys’ FirstDegree Semantics”,Australasian Journal of Philosophy,52: 105–120.
Kroon, F., 2019, “Routley’s Second Thoughts”, inD. Hyde (ed.), \emph{Noneist Explorations I: The Sylvan Jungle}(Volume 2), Cham: Springer, pp. 383–403.
–––, 2008, “Much Ado about Nothing: Priestand the Reinvention of Noneism”,Philosophy andPhenomenological Research, 76: 199–207.
Lamb, R., 2018, “The Last Man”, AustralasianJournal of Logic, 15(2): 513–592.
Lambert, K., 1968, “On the No Type Theory ofSignificance”,Australasian Journal of Philosophy, 46:79–86.
–––, 1976, “On ‘The Durability OfImpossible Objects’”,Inquiry, 19:251–254.
Lee, D.C., 1982, “Toward a Marxian Ecological Ethic: AResponse To Two Critics”,Environmental Ethics, 4:339–344.
Leopold, A., 1966,A Sand County Almanac:With Essayson Conservation from Round River, New York: Random House.
Lewis, D., 1990, “Noneism or Allism?”,Mind,99: 24–31.
–––, 1999, “Letters to Beall andPriest”, in Priestet al. 2004, pp. 176–177.
Lo, Y.S., 2006, “Making and Finding Values in Nature: From aHumean Point of View”,Inquiry, 49: 123–147.
Mannison, D., 1980, “A Critique of a Proposal for an‘Environmental Ethic’: Just Why is it‘Bad’ to Live in a ‘Concrete Jungle’?”in Mannison and McRobbie 1980, pp. 52–64.
Mannison, D. and McRobbie, M., 1980, “Introduction”,in D. Mannison, M. McRobbie and R. Routley (eds.),EnvironmentalPhilosophy, Department of Philosophy Monograph Series #2,Research School of Social Sciences, Australian National University,pp. 1–7.
Mares, E., 2004,Relevant Logic: A PhilosophicalInterpretation, Cambridge: Cambridge University Press.
–––, 2019, “The Universality ofRelevance”, in Weber (ed.) 2019, pp. 135–160.
Meyer, B., 1996, “Sylvan, Richard (1935–1996)”,Obituaries Australia (National Centre of Biography),Australian National University,available online, originally published inANU Reporter, 17 July 1996, p. 11original available online.
Mortensen, C., 1995,Inconsistent Mathematics (KluwerMathematics and Its Applications Series), Dordrecht: Kluwer.
–––, 2010,Inconsistent Geometry(Studies in Logic, Volume 27), London: College Publications(King’s College).
Motoarca, I.-R., 2014, “Fictional Surrogates”,Philosophia, 42: 1033–1053.
Naess, A., 1973, “The Shallow and the Deep, Long-RangeEcology Movement”,Inquiry, 16: 95–100.
Nolan, D., 2007, “A Consistent Reading of Sylvan’sBox”,Philosophical Quarterly, 57: 667–673.
–––, 2018, “Reflections on Routley’sUltralogic Program”, in Casatiet al. 2018, pp.407–430.
–––, 2013, “Impossible Worlds”,Philosophy Compass, 8: 360–372.
Nozick, R., 2013,Anarchy, State and Utopia, New York:Basic Books Publisher.
Nussbaum, M., 2007,Frontiers of Justice: Disability,Nationality, Species Membership, Cambridge, MA: HarvardUniversity Press.
Paolini Paoletti, M., 2013, “Exploring Meinong’sJungle and Beyond: an Investigation of Noneism and The Theory ofItems”,Humana Mente, 25: 275–291.
Parsons, T., 1978, “Nuclear and Extranuclear Properties,Meinong, and Leibniz”,Noûs, 12:137–152.
–––, 1980,Nonexistent Objects, NewHaven: Yale University Press.
–––, 1983, “Exploring Meinong’sJungle and Beyond by Richard Routley”,Journal ofPhilosophy, 80: 173–179.
Paske, G.H., 1991, “In Defense of Human Chauvinism: AResponse to R. Routley and V. Routley”,Journal of ValueInquiry, 25: 279–286.
Passmore, J., 1974,Man’s Responsibility ForNature, Duckworth.
Petersen, M. and Sandin, P., 2013, “The Last Man ArgumentRevisited”,Journal of Value Inquiry, 47:121–133.
Priest, G., 1997, “Sylvan’s Box: A Short Story And TenMorals”,Notre Dame Journal of Formal Logic, 38:573–582.
–––, 2000, “Objects of Thought”,Australasian Journal of Philosophy, 78: 494–502.
–––, 2003, “Meinongianism and thePhilosophy of Mathematics”,Philosophia Mathematica,11: 3–15.
–––, 2005,Towards Non-Being: The Logic andMetaphysics of Intentionality, Oxford: Oxford UniversityPress.
–––, 1987 [2006],In Contradiction,second edition, Oxford: Oxford University Press; first edition,1987.
–––, 2008,An Introduction to Non-ClassicalLogic, Cambridge: Cambridge University Press.
–––, 2014a,One: Being an Investigation intothe Unity of Reality and of its Part, Including the Singular Objectwhich is Nothingness, Oxford: Oxford University Press.
–––, 2014b, “Much Ado aboutNothing”,Australasian Journal of Logic, 1:146–158.
Priest, G., Beall, J.C. and Armour-Garb, B., 2004,The Law ofNon-Contradiction, Oxford: Oxford University Press.
Rapaport, W.J., 1984, “Exploring Meinong’s Jungleand Beyond by Richard Routley”,Philosophy andPhenomenological Research, 44: 539–552.
Read, S., 1988,Relevant Logic, Oxford: Blackwell.
Restall, G., 1999, “Negation in Relevant Logics: How IStopped Worrying and Learned to Love the Routley Star” inWhat is Negation?, edited by D. Gabbay and H. Wansing,Dordrecht: Kluwer Academic Publishers, pp. 53–76.
Ripley, D., 2012, “Structures and Circumstances: Two Ways toFine-Grain Propositions”,Synthese, 189(1):97–118.
Rolston, H., 1975, “Is There an Ecological Ethic?”,Ethics, 85: 93–109.
Rosenbaum, S.E., 1977, “The Property Objection and thePrinciple Of Identity”,Philosophical Studies, 32:155–164.
Routley, V., 1975, “Critical Notice of Passmore,Man’s Responsibility for Nature”,Australasian Journal of Philosophy, 53: 171–85.
Russell, B., 1905, “On Denoting”,Mind, 14:436–439.
–––, 1907, “Review of A. Meinong,Uberdie Stellung der Gegenstandstheorie im System derWissenschaften”,Mind, 16: 436–439.
Russell, G., 2008, “One True Logic?”,Journal ofPhilosophical Logic, 37: 593–611.
Smart, J.J.C., 1977, “A Critique of MeinongianSemantics”, in Hyde (ed.) 2019, 343–352.
Smiley, T. and Priest, G., 1993, “Can Contradictions beTrue?”,Proceedings of the Aristotelian Society(Supplementary Volume), 67(1): 17–54.
Szmuc, D. and Omori, H., 2018, “A Note on Goddard andRoutley’s Significance Logics”,Australasian Journal ofLogic, 15(2): 431–448.
Thomas, M., 2015, “A Generalization of the Routley-MeyerSemantic Framework”,Journal of Philosophical Logic,44: 411–427.
Thompson, J., 1990, “A Refutation of EnvironmentalEthics”,Environmental Ethics, 12: 147–160.
Urquhart, A., 1972, “Semantics for Relevant Logics”,Journal of Symbolic Logic, 37: 159–169.
Van Benthem, J.F.A.K., 1979, “What Is DialecticalLogic?”,Erkenntnis, 14: 333–347.
Von Solodkoff, T. and Woodward, R., 2013, “Noneism,Ontology, and Fundamentality”,Philosophy AndPhenomenological Research, 87: 558–583.
Warren, M.A., 1983, “The Rights of the Nonhuman World”in R. Elliot and A. Gare (eds.),Environmental Philosophy,London: Open University Press.
Weber, Z., 2012, “Transfinite Cardinals in ParaconsistentSet Theory”,Review of Symbolic Logic, 5(2):269–293.
–––, 2016, “Paraconsistent Computation andDialetheic Machines”, in Holger Andreas and Peter Verdee (eds.),Logical Studies of Paraconsistent Reasoning in Science andMathematics, Cham: Springer.
–––, 2017a, “Intrinsic Value and the LastLast Man”,Ratio, 30: 165–180.
–––, 2017b,“A guide to pluralism fornon-logicians”,Think, 16: 93–114.
–––, 2022,Paraconsistency inMathematics, Cambridge: Cambridge Elements, Cambridge UniversityPress.
Witherall, A., 2000, “Lewis And Sylvan On Noneism”,Grazer Philosophische Studien, 58–59:181–202.

Academic Tools

How to cite this entry.
Preview the PDF version of this entry at theFriends of the SEP Society.
Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO).
Enhanced bibliography for this entryatPhilPapers, with links to its database.

Other Internet Resources

Orton, D., 2005, “Ten Influential Environmental Books”.

Acknowledgments

Thanks to Ross Brady, Naoya Fujikawa, Roger Lamb, Graham Priest, andthe referees for comments.

Open access to the SEP is made possible by a world-wide funding initiative.
The Encyclopedia Now Needs Your Support
Please Read How You Can Help Keep the Encyclopedia Free

Browse

About

Support SEP

Mirror Sites

View this site from another server:

USA (Main Site)Philosophy, Stanford University

Info about mirror sites

Library of Congress Catalog Data: ISSN 1095-5054

Movatterモバイル変換