Free logics are a family of first-order logics which came about as a result of examining the existence assumptions of classical logic (Hintikka _The Journal of Philosophy_, _56_, 125–137 1959 ; Lambert _Notre Dame Journal of Formal Logic_, _8_, 133–144 1967, 1997, 2001 ). What those assumptions are varies, but the central ones are that (i) the domain of interpretation is not empty, (ii) every name denotes exactly one object in the domain and (iii) the quantifiers have existential (...) import. Free logics reject the claim that names need to denote in (ii). _Positive_ free logic concedes that some atomic formulas containing non-denoting names (including self-identity) are true, _negative_ free logic treats them as uniformly false, and _neutral_ free logic as taking a third value. There has been a renewed interest in analyzing proof theory of free logic in recent years, based on intuitionistic logic in Maffezioli and Orlandelli (_Bulletin of the Section of Logic_, _48_(2), 137–158 2019 ) as well as classical logic in Pavlović and Gratzl (_Journal of Philosophical Logic_, _50_, 117–148 2021 ), there for the positive and negative variants. While the latter streamlines the presentation of free logics and offers a more unified approach to the variants under consideration, it does not cover neutral free logic, since there is some lack of both clear formal intuitions on the semantic status of formulas with empty names, as well as a satisfying account of the conditional in this context. We discuss extending the results to this third major variant of free logics. We present a series of G3 sequent calculi adapted from Fjellstad (_Studia Logica_, _105_(1), 93–119 2017, _Journal of Applied Non-Classical Logics_, _30_(3), 272–289 2020 ), which possess all the desired structural properties of a good proof system, including admissibility of contraction and all versions of the cut rule. At the same time, we maintain the unified approach to free logics and moreover argue that greater clarity of intuitions is achieved once neutral free logic is conceptualized as consisting of two sub-varieties. (shrink)

I argue that neutral free logic and existence hedging are incompatible. Primarily, I respond to proposals by James Pryor intended to reconcile the two. Consideration of those proposals will reveal that on any neutral free logic either some existence hedges will entail some undesired existence claims, or they will not entail some desired existence claims.

Semantic externalism in the style of McDowell and Evans faces a puzzle formulated by Pryor: to explain that a sentence such as 'Jack exists' is only a posteriori knowable, despite being logically entailed by the seemingly logical truth 'Jack is self-identical', and hence being itself a logical truth and therefore a priori knowable. Free logics can dissolve the puzzle. Moreover, Pryor has argued that the existentially hedged 'If Jack exists, then Jack is self-identical', when properly formalised, is a logical (...) truth in a system of neutral free logic and therefore a priori knowable, while it does not entail that Jack exists. The latter holds also for negative free logic. In response, Yeakel has argued that on any system of neutral free logic existence hedges will either entail some unwanted existence claims or they will not entail some wanted existence claims. The dilemma also holds for any non-positive free logic. It will be shown that the extension of one of the systems of neutral free logic with a truth operator escapes Yeakel's dilemma, whereas no other non-positive free logic when extended with the truth operator does the same (or it breaks quantifier exchangeability). (shrink)

In this paper I am concerned with an analysis of negative existential sentences that contain proper names only by using negative or neutral free logic. I will compare different versions of neutral free logic with the standard system of negative free logic (Burge, Sainsbury) and aim to defend my version of neutral free logic that I have labeled non-standard neutral free logic.

This paper asks which free logic a Fregean should adopt. It examines options within the tradition including Carnap’s (1956) chosen object theory, Lehmann’s (1994, 2002) strict Fregean free logic, Woodruff’s (1970) strong table about Boolean operators and Bencivenga’s (1986, 1991) supervaluational semantics. It argues for a neutral free logic in view of its proximity towards explaining natural languages. However, disagreeing with Lehmann, it claims a Fregean should adopt the strong table based on Frege’s (...) discussion on generality. Supervaluation uses strong table and aims to give it a semantic justification. However, supervaluation is in turn justified by convention or mental experiments, which Lehmann argues as inadequate. The paper proposes a new justification of supervaluation based on sense and two-dimensional semantics. The resulting model, coined Supervaluational Neutral Free Logic (SNFL), resolves many conflicts between Lehmann and Bencivenga while staying close with Frege’s discussions about non-denotation. It also provides new insights into the relations among truth, logical truth, and supervaluated truth (or supertruth, for short). (shrink)

In this paper I aim to defend a first‐order non‐discriminating property view concerning existence. The version of this view that I prefer is based on negative (or a specific neutral) free logic that treats the existence predicate as first‐order logical predicate. I will provide reasons why such a view is more plausible than a second‐order discriminating property view concerning existence and I will also discuss four challenges for the proposed view and provide solutions to them.

McKinsey-style incompatibilist arguments attempt to show that the thesis that subjects have privileged, a priori access to the contents of their thoughts is incompatible with semantic externalism. This incompatibility follows – it is urged – from the fact that these theses jointly entail an absurd conclusion, namely, the possibility of a priori knowledge of the world. In a recent paper I argued that a large and important class of such arguments exemplifies a dialectical failure: if they are valid, the putatively (...) absurd conclusion can be generated without the privileged access premise. Michael McKinsey has responded by arguing that the semantic externalist should adopt a neutral free logic invalidating a principle that my argument essentially relies on. I will say why the semantic commitments of the externalist are in tension with free logic, thereby vindicating my original argument. (shrink)

Free logics aim at freeing logic from existence assumptions by making them explicit, e.g., by adding an existence premisse to the antecedence of the classical axiom-schema of Universal Instantiation. Their historical development was motivated by the problem of empty singular terms, and that one of simple statements containing at least one such singular term: what is the referential status of such singular terms and what truth-value, if any, do such statemants have? Free logics can be classified with (...) regard to their respective answers to these problems. Negative free logics assume that non-existent objects cannot have any properties at all; hence, in particular, they cannot be self-identical or rotate. Positive free logics believe that non-existents can be self-identical according to the Leibnizian concept of identity. Neutral free logics think that statements of self-identity are truth-valueless because of the Fregean principle of compositionality. Since only in negative free logic, but not in positive free logic, two statements of the forms "a = a" and "E!a" are logically equivalent, one also can define only for NFL, but not for PFL, existence by self-identity. (shrink)

This article aims to present a Free Dialogic Logic [FDL] as a general framework for hypothesis generation in the practice of modelling in science. Our proposal is based on the idea that the inferential function that models fulfil during the modelling process (surrogate reasoning) should be carried out without ontological commitments. The starting point to achieve our objective is that the scientific consideration of models without a target is a symptom that, on the one hand, the Applicability of (...) Logic should be considered among the conditions of adequacy that should take into account all modeling process and, on the other, that the inferential apparatus at the base of the surrogate reasoning process must be rid of realistic assumptions that lead to erroneous conclusions. In this sense, we propose as an alternative an ontologically neutral inferential system in the perspective of dialogical pragmatism. (shrink)

Though largely unnoticed, in "Two Dogmas" Quine himself invokes a distinction: a distinction between logical and analytic truths. Unlike analytic statements equating 'bachelor' with 'unmarried man', strictly logical tautologies relating two word-tokens of the same word-type, e.g., 'bachelor' and 'bachelor' are true merely in virtue of basic phonological form, putatively an exclusively non-semantic function of perceptual categorization or brute stimulus behavior. Yet natural language phonemic categorization is not entirely free of interpretive semantic considerations. "Phonemic reductionism" in both its linguistic (...) and behavioral, Newbury Park, CA, Sage Publications, 164-167) guise is false. The semantic basis of phonological equivalence, however, has repercussions vis-à-vis Quine's critique of analyticity. A consistent rejection of meaning-based equivalencies eliminates not only analyticity, but imposes a form of phonological eliminativism too. Phonological eliminativism is the reductio result of applying Quinean meaning skepticism to the phonological typing of natural language. But unlike analyticity, phonology is presumably not subject to philosophical dismissal. The semantic basis of natural language phonology serves to neutralize Quine's argument against analyticity: without the semantics of meaning, more than just synonymy is lost; basic phonology must also be forfeited. (shrink)

This book defends the Direct Reference (DR) thesis in philosophy of language regarding proper names and indexical pronouns. It uniquely draws out the significant consequences of DR when it is conjoined with the fact that these singular terms sometimes fail to refer. Even though DR is widely endorsed by philosophers of language, many philosophically important and radically controversial consequences of the thesis have gone largely unexplored. This book makes an important contribution to the DR literature by explicitly addressing the consequences (...) that follow from DR regarding failure of reference. Michael McKinsey argues that only a form of neutral free logic can capture a revised concept of logical truth that is consistent with the fact that any sentence of any form that contains a directly referring genuine term can fail to be either true or false on interpretations where that term fails to refer. He also explains how it is possible for there to be true (or false) sentences that contain non-referring names, even though this possibility seems inconsistent with DR. Consequences of Reference Failure will be of interest to philosophers of language and logic and linguists working on Direct Reference. (shrink)

From Leibniz to Krauss philosophers and scientists have raised the question as to why there is something rather than nothing. Why-questions request a type of explanation and this is often thought to include a deductive component. With classical logic in the background only trivial answers are forthcoming. With free logics in the background, be they of the negative, positive or neutral variety, only question-begging answers are to be expected. The same conclusion is reached for the modal version (...) of the Question, namely ‘Why is there something contingent rather than nothing contingent?’. The categorial version of the Question, namely ‘Why is there something concrete rather than nothing concrete?’, is also discussed. The conclusion is reached that deductive explanations are question-begging, whether one works with classical logic or positive or negative free logic. I also look skeptically at the prospects of giving causal-counterfactual or probabilistic answers to the Question, although the discussion of the options is less comprehensive and the conclusions are more tentative. The meta-question, viz. ‘Should we not stop asking the Question’, is accordingly tentatively answered affirmatively. (shrink)

Motivations for systems of free logics are reviewed and systems are divided according as they are positive (asserting atomic truths with non-denoting terms) negative (denying all such sentences) or neutral. A positive theory is developed and defended. One of the major considerations in favor of the theory is that it allows (via translation) representation of the other points of view. Finally, the relation between free logic and truth theories is elaborated.

Alexius Meinong nimmt in der Geschichte der Ontologie eine ausgezeichnete Stellung ein. Er war der erste Philosoph, der in systematischer Weise eine quasi-onto¬logische Disziplin entwickelte, die im Vergleich zu der Disziplin, die man traditionell Metaphysik oder Ontologie nennt, viel allgemeiner sein sollte. Die Metaphysik untersucht das Seiende als Seiendes, und die seienden Entitäten bilden – so die These Meinongs – nur ein kleines Fragment dessen, was man unter dem Namen „Gegenstands¬theorie” untersuchen kann. Die Gegenstände als solche sind „außerseiend”, d.h. sie (...) sind bezüg¬lich ihres Seins bzw. Nicht-Seins neutral. Es gibt drei prima facie plausible Möglichkeiten, wie man die Meinongsche Seinsneutralität verstehen kann. Die Meinongsche Philosophie kann als (i) eine Erweiterung der Ontologie, als (ii) eine onto¬logisch nicht-verpflich¬tende Deutung von Quantoren oder als (iii) eine Version der free logic interpretiert werden. (shrink)

The subtitle of this text intended for philosophy students’ 2nd course in logic is in no way misleading. It is a lucid introduction to the philosophic activities of uncovering metaphysical presuppositions of logical techniques and altering logical techniques, and hence assessments of deductive validity, to conform to metaphysical presuppositions. They do not, though, assume that techniques for assessing deductive validity are or should be wholly dependent upon metaphysical presuppositions. They write on p. 213 in their section on intensional discourse: (...) "And logic wherever possible ought not to wait upon philosophy, for logic wherever possible ought to be neutral between different philosophical analyses." In their investigations of metaphysical presuppositions and logical techniques, they consider primarily the consequences of existential presuppositions about the use of singular terms, viz., individual variables, individual names, and definite descriptions. They favor freeing use of singular terms from existential presuppositions. The consideration of allowing non-referring names and definite descriptions makes their text one of the first, if not the first, for teaching Free Logic. The gist of Free Logic is not to allow existential generalization of Fb to unless there is an auxiliary premise asserting the existence of b, because use of the name b has been freed from the presupposition that it names something. It is suitable that these authors have a text on Free Logic since Lambert is the major figure in its origin while van Fraassen has established some of the most significant results about Free Logic systems. They go on to consider alternative logical rules to those of Russell for dealing with nonreferring definite descriptions. These alternatives to standard logic are philosophically motivated. They are not simply dumped upon students as rules for symbol manipulation. For instance, on pp. 152-157 they give a succinct analysis of the Russell-Meinong debate when they agree with Meinong that one can talk of the thing that is such and such without accepting that there is such a thing. The treatment of singular terms leads them to discussions of topics such as: What is it for a logic to be extensional and is Free Logic extensional?, the substitution interpretation of quantifiers, and the notion of presupposition. (shrink)

One of Frege’s basic philosophical convictions has been that “a large part of the philosopher’s work consists—or at least should consist—in a fight against language.”. Besides, it is partly to his having yielded too easily to the deceptive suggestions of natural language that he himself attibuted, at the very end of his life, the failure of his attempt at defining numbers in logicist terms Nevertheless, he remained to the end convinced that the hopes raised by logic, one of whose (...) tasks is “to free us of the chains of language”, can only rest, in the last analysis, upon the possibility to trust the bulk of language and to make use of “such an imperfect instrument” to fight from the inside the uncertain fight that the philosopher must embark upon in order to free himself from its dominion and neutralize or eliminate its most damaging imperfections. (shrink)

This article is devoted to the analysis of arguments from empirical science against free will. Its main purpose is to reveal their deep anti-naturalism. This anti-naturalism lies in the use of a concept of free will that cannot be the subject of naturalistic consideration, as well as in the various explanatory and ontological paradoxes that arguments from empirical science lead in case when someone is trying to generalize the explanatory principles underlying them. At the beginning of the article, (...) the author gives a general notion of the free will problem, a working definition of naturalism and the place of arguments from empirical science in discussions about free will. To achieve the main goal of the article, the author suggests a classification of arguments from empirical science, which includes five types: from prediction, from manipulation, from the brain, from illusion, from the substitution of concepts. In accordance with this classification, the structure of the article is defined, where each of the presented types is sequentially considered. The logic of considering each type of argument is approximately the same: explication of the essence of the argument of a particular type, its analysis, identification of basic principles and their generalization, demonstration of the negative consequences that it leads to, and answers to possible objections. In the course of the consideration, the author formulates an ontologically neutral concept of free will as a set of abilities associated with the agent’s control over his actions. At the end of the article, the main points is summed up, the idea of naturalistic compatibilism is proposed, the role of arguments from empirical science in discussions about free will is clarified, as is the problem of free will itself, the question of the sources of “chimerization” of naturalism is briefly highlighted, and the problem of completeness of the proposed reasoning is touched upon. (shrink)

Halbach has argued that Tarski biconditionals are not ontologically conservative over classical logic, but his argument is undermined by the fact that he cannot include a theory of arithmetic, which functions as a theory of syntax. This article is an improvement on Halbach's argument. By adding the Tarski biconditionals to inclusive negative free logic and the universal closure of minimal arithmetic, which is by itself an ontologically neutral combination, one can prove that at least one thing (...) exists. The result can then be strengthened to the conclusion that infinitely many things exist. Those things are not just all Gödel codes of sentences but rather all natural numbers. Against this background inclusive negative free logic collapses into noninclusive free logic, which collapses into classical logic. The consequences for ontological deflationism with respect to truth are discussed. (shrink)

In a recent discussion article in this journal, Gila Sher responds to some of my criticisms of her work on what she calls the formal-structural account of logical consequence. In the present paper I reply and attempt to advance the discussion in a constructive way. Unfortunately, Sher seems to have not fully understood my 1997. Several of the defenses she mounts in her 2001 are aimed at views I do not hold and did not advance in my 1997. Most prominent (...) among these are her claims that I reject the formal-structural account, because it licenses “unnatural” logical constants, and that I consider the “truth-functional criterion” for connectives “a paradigm of a successful criterion of logicality”. Both of these claims are simply false, as even a moderately careful reading of my 1997 will show. Other charges she makes have some basis in fact but are inaccurate. For example, she says that I claim that FS is “neutral with regard to the apriority of logic,” and that this neutrality “renders it inconsistent”. What I actually say is that Sher’s acceptance of the neutrality in question is “inconsistent with part of the legacy of Tarski, a legacy that she finds very congenial”, not that FS itself is inconsistent. More interestingly, she misunderstands my claim about the apriority of logic, and clarification of this misunderstanding suggests two distinct ways in which logic might be held to be free of empirical influence. It is also noteworthy that Sher’s statements about the apriority of logic constitute both a change in the position she took in her 1991 and, although she seems not to realize it, an admission that she does not take issue with one of my major criticisms. (shrink)

Free logic is an important field of philosophical logic that first appeared in the 1950s. J. Karel Lambert was one of its founders and coined the term itself. The essays in this collection explore the philosophical foundations of free logic and its application to areas as diverse as the philosophy of religion and computer science. Amongst the applications on offer are those to the analysis of existence statements, to definite descriptions and to partial functions. The (...) volume contains a proof that free logics of any kind are non-extensional and then uses that proof to show that Quine's theory of predication and referential transparency must fail. The purpose of this collection is to bring an important body of work to the attention of a new generation of professional philosophers, computer scientists and mathematicians. (shrink)

This dissertation explains and defends Hegel's "dialectical" logic and the useful critical and normative contributions it can make to philosophy and some aspects of life. Hegel's logic investigates metaphysical "logical" determinations which constitute the structural principles of everything generally, but his context-neutral conception of logical structures and his non arbitrary method sets him favorably apart from other philosophies. It dispenses with the issue whether metaphysics illegitimately projects the mental onto a pre-given world of experience, since even distinctions (...) like "mind versus matter" presuppose prior logical structures. These structures underly other philosophical programs, so Hegel's logic can play an explanatory and critical role against alternatives. Moreover, Hegel's logic neither presents insuperable methodological problems nor suggests absurd conclusions about topics like the law of noncontradiction. ;In Chapter Three I explain and develop Hegel's theory of truth as the correspondence of something's developed, actual existence to its own structural nature. Human thinking and activities especially exemplify truth, since humans have the ability to make themselves and their activities correspond most closely to what they ought to be. In his logic Hegel then provides a normative logical model for becoming a "true" human being: an intrapsychically integrated, normatively committed and free agent engaged constructively with one's social world. ;In Chapter Four I argue that speculative logic can solve and remain invulnerable to longstanding problems in traditional skepticism, especially the more powerful ancient type. Skepticism is effective because its arguments against philosophical claims are implicitly structured according to underlying logical determinations of the types Hegel describes. Skeptical conundrums correspond to the local opposition between the first two moments of dialectical triads, but I show that these moments are only two unintegrated halves of a superior logical structure. In this way, Hegel's logic is able to explain and beat skepticism on a deeper level. (shrink)

In this article, we argue for the distinction of three different types of predicates: existence entailing, (existence) neutral, and nonexistence entailing predicates. We provide linguistic tests as well as examples to motivate this distinction. After motivating our views on predicates, we show how our theory is able to deal with a multitude of problematic data both known from the literature as well as new. Then, we develop a multi-domain predicate logic inspired by certain versions of free logics (...) in order to represent these entailments in a formal way. (shrink)

Free logic - i.e., logic free of existential presuppositions in general and with respect to singular terms in particular- began to come into its own as a field of research in the 1950s. As is the case with so many developments in Western philosophy, its roots can be traced back to ancient Greek philo sophy. It is only during the last fifty years, however, that it has become well established as a branch of modern logic. (...) The name of Karel Lambert is most closely connected with this development: he gave it its name and its profile as a well defined field of research. After a development of fifty years, it is time to look back and take stock while at the same time scanning for new perspectives. This is the purpose of the papers collected in this volume. The first paper is written by Karel Lambert himself who also comments on all the papers of the other authors. In an introductory essay we give a survey of the present status of and new directions in free logic. (shrink)

Classical logic assumes that names are univocal: Every name refers to exactly one existing individual. This Principle of Univocality has two parts: an existence assumption and a uniqueness assumption. The existence assumption holds that every name refers to at least one individual, and the uniqueness assumption states that every name refers to at most one individual. Various systems of free logic which have been developed and studied since the 1960s relax the existence assumption, but retain the uniqueness (...) assumption. The present work investigates violations of both halves of the Principle of Univocality. That is, whereas the free logics developed from the 1960s are called 'free' because they are free of existential assumptions, the current Element generalizes this idea, to study logics that are free of uniqueness assumptions. It explores several versions of free logic, comparing their advantages and disadvantages. Applications of free logic to other areas of philosophy are explored. (shrink)

Starting from a generalization of the standard axioms for a monoid we present a stepwise development of various, mutually equivalent foundational axiom systems for category theory. Our axiom sets have been formalized in the Isabelle/HOL interactive proof assistant, and this formalization utilizes a semantically correct embedding of free logic in classical higher-order logic. The modeling and formal analysis of our axiom sets has been significantly supported by series of experiments with automated reasoning tools integrated with Isabelle/HOL. We (...) also address the relation of our axiom systems to alternative proposals from the literature, including an axiom set proposed by Freyd and Scedrov for which we reveal a technical issue (when encoded in free logic where free variables range over defined and undefined objects): either all operations, e.g. morphism composition, are total or their axiom system is inconsistent. The repair for this problem is quite straightforward, however. (shrink)

One of the striking features of Logical Investigations is its metaphysical neutrality. What are the implications of this neutrality? Should it be counted among the many virtues of the work, or rather mourned as a fateful shortcoming? In an article published in the beginning of the nineties, I answered this question rather unequivocally. At that time I considered the neutrality in question to be highly problematic. In the meantime, however, I have had the pleasure of reading Jocelyn Benoist’s recent work (...) Phénoménologie, sémantique, ontologie, where he argues for the opposite conclusion, criticizing my own interpretation in the process. In the light of this criticism, I would like to use this occasion to reconsider the question anew. (shrink)

Evans envisaged a language containing both Russellian and descriptive names. A language with descriptive names, which can contribute to truth conditions even if they have no bearer, needs a free logical truth theory. But a metalanguage with this logic threatens to emasculate Russellian names. The paper details this problem and shows, on Evans's behalf, how it might be resolved.

Free logic, an alternative to traditional logic, has been seen as a useful avenue of approach to a number of philosophical issues of contemporary interest. In this collection, Karel Lambert, one of the pioneers in, and the most prominent exponent of, free logic, brings together a variety of published essays bearing on the application of free logic to philosophical topics ranging from set theory and logic to metaphysics and the philosophy of religion. (...) The work of such distinguished philosophers as Bas van Fraassen, Dana Scott, Tyler Burge, and Jaakko Hintikka is represented. Lambert provides an introductory essay placing free logic in the logical tradition beginning with Aristotle, developing it as the natural culmination of a trend begun in the Port Royal logic of the 1600s, and continuing through current predicate logic--the trend to rid logic of existence assumptions. His Introduction also provides a useful systematic overview of free logic, including both a standard syntax and some semantical options. (shrink)

The paper presents a uniform proof-theoretic treatment of several kinds of free logic, including the logics of existence and definedness applied in constructive mathematics and computer science, and called here quasi-free logics. All free and quasi-free logics considered are formalised in the framework of sequent calculus, the latter for the first time. It is shown that in all cases remarkable simplifications of the starting systems are possible due to the special rule dealing with identity and (...) existence predicate. Cut elimination is proved in a constructive way for sequent calculi adequate for all logics under consideration. (shrink)

This paper proves normalisation theorems for intuitionist and classical negative free logic, without and with the $\invertediota$ operator for definite descriptions. Rules specific to free logic give rise to new kinds of maximal formulas additional to those familiar from standard intuitionist and classical logic. When $\invertediota$ is added it must be ensured that reduction procedures involving replacements of parameters by terms do not introduce new maximal formulas of higher degree than the ones removed. The problem (...) is solved by a rule that permits restricting these terms in the rules for $\forall$, $\exists$ and $\invertediota$ to parameters or constants. A restricted subformula property for deductions in systems without $\invertediota$ is considered. It is improved upon by an alternative formalisation of free logic building on an idea of Ja\'skowski's. In the classical system the rules for $\invertediota$ require treatment known from normalisation for classical logic with $\lor$ or $\exists$. The philosophical significance of the results is also indicated. (shrink)

The expression ‘free logic,’ coined by the author in 1960, is an abbreviation for ‘logic free of existence assumptions with respect to its terms, singular and general, but whose quantifiers are treated exactly as in standard quantifier logic.’ In more traditional language, such logics do not presume that either singular or general terms — the two distinct categories of terms emphasized in modern logical grammar — have existential import. A singular term ‘t’ has existential import (...) just in case t exists (or, equivalently, there exists an object the same as t) and a general term (or predicate) ‘G’ has existential import just in case G exist (or, equivalently, there exists an object that is G).1 Examples from colloquial English customarily taken to be singular terms are expressions such as ‘Socrates’, ‘the planet causing perturbations in the orbit of Mercury’, ‘5’, ‘5/0’, ‘the square of 3’ and ‘having a heart’. Some of these do not have existential import — in particular, ‘5/0’ and ‘the planet causing perturbations in the orbit of Mercury’. Examples from colloquial English customarily taken to be general terms are expressions such as ‘is a philosopher’, ‘is a planet causing perturbations in the orbit of Mercury’, ‘number’, ‘is divisible by 0’, and ‘has a heart’. Some of these general terms do not have existential import — in particular, ‘is a planet causing perturbations in the orbit of Mercury’ and ‘is divisible by 0’. To say that the quantifers are treated exactly as in standard quantifier logic is to say, roughly, that the operator symbol ‘∃’ (the existential quantifier) reads: ‘There exists an object’, and the operator symbol ‘∀’ (the universal quantifier) reads: ‘Every existent object’. (shrink)

Linnebo and Shapiro have recently given an analysis of potential infinity using modal logic. A key technical component of their account is to show that under a suitable translation ◊ of nonmodal language into modal language, nonmodal sentences ϕ 1, …, ϕ n entail ψ just in case ϕ 1 ◊, …, ϕ n ◊ entail ψ ◊ in the modal logic S4.2. Linnebo and Shapiro establish this result in nonfree logic. In this note I argue that (...) their analysis of potential infinity should be carried out in a free logic. I then extend their key theorems to the setting of negative free logic. (shrink)

By a free logic is generally meant a variant of classical first-order logic in which constant terms may, under interpretation, fail to refer to individuals in the domain D over which the bound variables range, either because they do not refer at all or because they refer to individuals outside D. If D is identified with what is assumed by the given interpretation to exist, in accord with Quine’s dictum that “to be is to be the value (...) of a [bound] variable,” then a free variation on classical semantics does not require that all constant terms refer to existents, and in this sense such terms lack existential import. (shrink)

The principle of universal instantiation plays a pivotal role both in the derivation of intensional paradoxes such as Prior’s paradox and Kaplan’s paradox and the debate between necessitism and contingentism. We outline a distinctively free logical approach to the intensional paradoxes and note how the free logical outlook allows one to distinguish two different, though allied themes in higher-order necessitism. We examine the costs of this solution and compare it with the more familiar ramificationist approaches to higher-order (...) class='Hi'>logic. Our assessment of both approaches is largely pessimistic, and we remain reluctantly inclined to take Prior’s and Kaplan’s derivations at face value. (shrink)

A new logic is presented without predicates—except equality. Yet its expressive power is the same as that of predicate logic, and relations can faithfully be represented in it. In this logic we also develop an alternative for set theory. There is a need for such a new approach, since we do not live in a world of sets and predicates, but rather in a world of things with relations between them.

This paper contains an axiomatic theory of first order modal logic with operations, identity, and descriptions together with a formal semantics which interprets the theory in such a manner that empty universes of discourse and denotationless terms are allowed for at each possible world. The intuitive basis of the theory is discussed in preliminary sections, the syntax and semantics of theory are then characterized, its semantical adequacy is demonstrated, and certain important axioms and theorems are discussed in detail in (...) later sections. (shrink)

In this paper, I will defend a new compositional semantics for single-domain free logic. This semantics makes use of a distinction between the semantic value of a singular term and its semantic referent. The semantic value of a singular term is conceived of as a set that either contains the semantic referent or no element at all. The semantic referent is the object that the term designates. Before I will introduce this new semantics for single-domain predicate and an (...) S5-type modal logic in detail, I will present five related problems of compositionality of the standard semantics for these logical systems. After that I will show in detail how my new proposed alternative semantics can be used to solve nearly all of the outlined five problems. (shrink)

A universally free logic is a system of quantification theory, with or without identity, whose theses remain logically true if the domain of quantification is empty and some of the singular terms present in the language do not denote existing objects. In the West, logics satisfying and ones satisfying were developed starting in the 1950s. But Stanisław Jaśkowski preceded all this work by some twenty years: his paper “On the Rules of Supposition in Formal Logic” of 1934 (...) can be regarded as containing, at least implicitly, the first universally free logic. The system proposed there is an inclusive logic as it is, and a straightforward extension of it is also free. (shrink)

This paper presents a bivalent extensional semantics for positive free logic without resorting to the philosophically questionable device of using models endowed with a separate domain of “non-existing” objects. The models here introduced have only one (possibly empty) domain, and a partial reference function for the singular terms (that might be undefined at some arguments). Such an approach provides a solution to an open problem put forward by Lambert, and can be viewed as supplying a version of parametrized (...) truth non unlike the notion of “truth at world” found in modal logic. A model theory is developed, establishing compactness, interpolation (implying a strong form of Beth definability), and completeness (with respect to a particular axiomatization). (shrink)

Peter Milne (2007) poses two challenges to the inferential theorist of meaning. This study responds to both. First, it argues that the method of natural deduction idealizes the essential details of correct informal deductive reasoning. Secondly, it explains how rules of inference in free logic can determine unique senses for the existential quantifier and the identity predicate. The final part of the investigation brings out an underlying order in a basic family of free logics.

Structurally free logic LC was introduced in [4]. A natural extension of LC, in particular, in a sequent formulation, is by conjunction and disjunction that do not distribute over each other. We define a set theoretical semantics for these logics via constructing a representation of a lattice that we extend by intensional operations. Canonically, minimally overlapping filter-ideal pairs are used; this construction avoids the use of an equivalent of the axiom of choice and lends transparency to the structure. (...) We also discuss adapting the present semantics for substructural logics, as well as, the question of cannnonicity of LC+. (shrink)

A 'Kripke-style' semantics is given for combinatory logic using frames with a ternary accessibility relation, much as in the Tourley-Meyer semantics for relevance logic. We prove by algebraic means a completeness theorem for combinatory logic, by proving a representation theorem for 'combinatory posets.' A philosophical interpretation is given of the models, showing that an element of a combinatory poset can be understood simultaneously as a set of states and as a set of actions on states. This double (...) interpretation allows for one such element to be applied to another . Application turns out to be modeled the same way as 'fusion' in relevance logic.We also introduce 'dual combinators' that apply from the right. We then explore relationships to some well-known substructural logics, showing that each can be embedded into the structurally free. non-associative Lambek calculus, with the embedding taking a theorem ω to a statement of the form Γ ⊨ ω, where Γ is some fusion of the combinators needed to justify the structural assumptions of the given substructural logic. This builds on earlier ideas from Belnap and Meyer about a Gentzen system wherein structural rules are replaced with rules for introducing combinators. We develop such a system and prove a cut theorem. (shrink)

Professor Tennant and I agree on much regarding the proof-theoretic semantics of free logic. Here I point to two issues, one on which we disagree, the other on which I find it hard to say how closely we may agree. The first concerns the exact content of Tennant's Rule of Atomic Denotation. The second concerns the nature of assumptions whose formal counterparts contain parametric occurrences of names.