Counterfactuals is David Lewis' forceful presentation of and sustained argument for a particular view about propositions which express contrary to fact conditionals, including his famous defense of realism about possible worlds and his theory of laws of nature.

This book, one of the first full-length studies of the modalities to emerge from the debate to which Saul Kripke, David Lewis, Ruth Marcus, and others are contributing, is an exploration and defense of the notion of modality de re, the idea that objects have both essential and accidental properties. Plantinga develops his argument by means of the notion of possible worlds and ranges over such key problems as the nature of essence, transworld identity, negative existential propositions, and the existence (...) of unactual objects in other possible worlds. He also applies his logical theories to the elucidation of two problems in the philosophy of religion: the problem of evil and the ontological argument. (shrink)

It is my aim in this paper to show that the contemporary assimilation of essence to modality is fundamentally misguided and that, as a consequence, the corresponding conception of metaphysics should be given up. It is not my view that the modal account fails to capture anything which might reasonably be called a concept of essence. My point, rather, is that the notion of essence which is of central importance to the metaphysics of identity is not to be understood in (...) modal terms or even to be regarded as extensionally equivalent to a modal notion. The one notion is, if I am right, a highly refined version of the other; it is like a sieve which performs a similar function but with a much finer mesh. (shrink)

This long-awaited book replaces Hughes and Cresswell's two classic studies of modal logic: _An Introduction to Modal Logic_ and _A Companion to Modal Logic_. _A New Introduction to Modal Logic_ is an entirely new work, completely re-written by the authors. They have incorporated all the new developments that have taken place since 1968 in both modal propositional logic and modal predicate logic, without sacrificing tha clarity of exposition and approachability that were essential features of their earlier works. The book takes (...) readers from the most basic systems of modal propositional logic right up to systems of modal predicate with identity. It covers both technical developments such as completeness and incompleteness, and finite and infinite models, and their philosophical applications, especially in the area of modal predicate logic. (shrink)

are synthetic a priori judgements possible?" In both cases, i~thas usually been t'aken for granted in fife one case by Kant that synthetic a priori judgements were possible, and in the other case in contemporary,'d-". philosophical literature that contingent statements of identity are ppss. ible. I do not intend to deal with the Kantian question except to mention:ssj~".

Analytic philosophy has recently demonstrated a revived interest in metaphysical problems about possibility and necessity. Graeme Forbes here provides a careful description of the logical background of recent work in this area for those who may be unfamiliar with it, moving on to d discuss the distinction between modality de re and modality de dicto and the ontological commitments of possible worlds semantics. In addition, Forbes offers a unified theory of the essential properties of sets, organisms, artefacts, substances, and events, (...) based on the doctrine that identity facts must be intrinsically grounded, and analyzes and rejects apparent counterexamples to this doctrine. (shrink)

In this paper, I formulate, elucidate, and defend a version of modal realism with overlap, the view that objects are literally present at more than one possible world. The version that I defend has several interesting features: (i) it is committed to an ontological distinction between regions of spacetime and material objects; (ii) it is committed to compositional pluralism, which is the doctrine that there is more than one fundamental part-whole relation; and (iii) it is the modal analogue of endurantism, (...) which is the doctrine that objects persist through time by being wholly present at each moment they are located. (shrink)

Actualism is the doctrine that the only things there are, that have being in any sense, are the things that actually exist. In particular, actualism eschews possibilism, the doctrine that there are merely possible objects. It is widely held that one cannot both be an actualist and at the same time take possible world semantics seriously — that is, take it as the basis for a genuine theory of truth for modal languages, or look to it for insight into the (...) modal structure of reality. For possible world semantics, it is supposed, commits one to possibilism. In this paper I take issue with this view. To the contrary, I argue that one can take possible world semantics seriously without any commitment to possible worlds or possibilism and hence remain in full compliance with actualist scruples. Moreover, one can do so without without invoking either "ersatz" worlds or haecceities. (shrink)

In a recent article in Analysis, Graeme Hunter and William Seager (1981) attempt to rescue counterpart theory (CT) from some objections of Hazen 1979. They see these objections as arising from ‘uncritical use of the translation scheme originally proposed by Lewis’, and intend to meet them by refraining from use of that scheme. But they do not offer a new scheme; they say ‘…it is no more necessary to have one to capture the sense of modal idiom than it is (...) to capture the sense of quantificational idiom…Appeal to truth value is the single most important criterion of correct translation’ (Hunter and Seager 1981:72). Thus, where the scheme of Lewis (1968) translates a truth by a falsehood or conversely, Hunter and Seager simply produce a sentence which they claim to be a better translation, without articulating any structural principles they employ to arrive at their candidate. A friend of CT should not be happy with this procedure. Let Lm be first-order modal language and Lc be the language of counterpart theory. Sentences of Lc are intended to interpret or elucidate the meanings of Lm-sentences in the strong sense that they should be the outputs of an adequate theory of meaning, which we can formulate as a model theory, for Lm, written in Lc plus set theory. The interest of CT resides in its potential to provide an alternative approach to the model theory of modal logic, and from the clauses of any such alternative model theory we should be able to read off a translation scheme for Lm into Lc, just as we can in the standard case. If CT’s motivation is sound, which Hunter and Seager do not dispute, yet there is no translation scheme and so no counterpart-theoretic model theory, one might suspect some defect in the original language Lm. And in fact, Hunter and Seager find certain Lm-sentences multiply ambiguous with respect to Lc; but if a counterpart-theoretic model theory is possible, to say.. (shrink)

Here I propose a coherent way of preserving the identity of material objects with the matter that constitutes them. The presentation is formal, and intended for RSL. An informal presentation is in preliminary draft! -/- Relative-sameness relations—such as being the same person as—are like David Lewis's "counterpart" relations in the following respects: (i) they may hold between objects that aren't identical (I propose), and (ii) there are a multiplicity of them, different ones of which may be variously invoked in different (...) contexts. They differ from counterpart relations, however, in that they are weak equivalence relations (transitive, symmetric and weakly reflexive). The likenesses to counterpart relations make them suitable for an analysis of de-re temporal and modal predications. The difference renders the resulting counterpart theory immune to standard criticisms of Lewis's Counterpart Theory (e.g., in Hazen 1979, and Fara and Williamson 2005). (shrink)

First - order modal logic is very much under current development, with many different semantics proposed. The use of rigid objects goes back to Saul Kripke. More recently, several semantics based on counterparts have been examined, in a development that goes back to David Lewis. There is yet another line of research, using intensional objects, that traces back to Richard Montague. I have been involved with this line of development for some time. In the present paper, I briefly sketch several (...) of the approaches to first - order modal logic. Then I present one that I call FOIL in the Montague tradition that, I believe, is both expressive and natural. I briefly discuss in what sense it can be made to encompass the other approaches. Finally, I provide tableau rules to go with the FOIL semantics. (shrink)

This paper presents and motivates a counterpart theoretic semantics for quantifi ed modal logic based on a fleshed out account of Lewis's notion of a `possibility.' According to the account a possibility consists of a world and some haecceitistic information about how each possible individual gets represented de re. A semantics for quanti ed modal logic based on evaluating formulae at possibilities is developed. It is shown that this framework naturally accommodates an actuality operator, addressing recent objections to counterpart theory, (...) and is equivalent to the more familiar Kripke semantics for quanti fied modal logic with an actuality operator. (shrink)

The paper investigates the link between the theory of modal occurrents (where individuals are allowed to stretch across possible worlds) and Lewis’s counterpart theory (where all individuals are world-bound but have counterparts in other worlds). First I show how to interpret modal talk extensionally within the theory of modal occurrents. Then I show that the assumption that worlds be pairwise discrete is all that is needed to reconstruct the bulk of counterpart theory (i.e., to define the concept of a counterpart (...) and to derive the standard postulates governing that concept) in terms of the theory of modal occurrents. Finally, I argue that this reconstruction allows us to view the indeterminacy of our modal intuitions as being part and parcel with the indeterminacy of our criteria for individuating modal occurrents, and that this indeterminacy is naturally explained in terms of linguistic (as opposed to ontic) vagueness. (shrink)

David Lewis's modal realism claims that nothing can exist in more than one world or time, and that statements about how something would have been are to be analysed in terms of its counterpart. I first explain why the counterpart relation depends on de re modal statements in an intensional language, so that intuitive properties of similarity relations cannot be used to show that the counterpart relation is not an equivalence relation. I then look at test sentences in (the intensional) (...) natural language, and show that none of them provide compelling evidence that a counterpart semantics is needed. (shrink)

Possibilism—the view that there are non-actual, merely possible entities—is a surprisingly resilient doctrine.1 One particularly hardy strand of possibilism—the modal realism championed by David Lewis—continues to attract both foes who seek to demonstrate its falsity (or at least stare its advocates into apostasy) and friends who hope to defend modal realism (or, when necessary, modify modal realism so as to avoid problematic objections).2 Although I am neither a foe nor friend of modal realism (but some of my best friends are!), (...) like many I continue to be fascinated by the doctrine. (shrink)

To reconcile true claims of de re necessity with the supposedly contingent existence of the concrete objects those claims are typically about, Kripkean essentialists invoke weak necessity. The claim that a is necessarily F is held to be equivalent to the claim that necessarily, if a exists then a is F. This strategy faces a barrage of serious objections a proper subset of which shows that the strategy fails to achieve its intended purpose. Relief can be provided via recourse to (...) a markedly non-Kripkean version of essentialism.1. (shrink)

Lewis proposed to test the validity of a modal thesis by checking whether its possible-world translation is a theorem of counterpart theory. However, that criterion fails to validate many standard modal laws, thus raising doubts about the logical adequacy of the Lewisian framework. The present paper considers systems of counterpart theory of increasing strength and shows how each can be motivated by exhibiting a suitable intended model. In particular, perfect counterpart theory validates all the desired modal laws and therefore provides (...) a way out of the logical objection. Finally, a weakening of perfect counterpart theory is put forward as a response to some metaphysical objections. (shrink)

Counterpart theory has many benefits, but few are happy to accept the metaphysical setting in which this account of de re modality was developed by its architect, David Lewis. I argue here that counterpart theory can be made acceptable by the lights of those who repudiate the existence of merely possible objects. To the "ersatz" counterpart theorist I offer two stories: one about the relate of the counterpart relation and one about the relation itself. With these in place, I then (...) defend ersatz counterpart theory from a number of objections that can be found in the literature. (shrink)

It has been argued that a combination of game-theoretic semantics and independence-friendly (IF) languages can provide a novel approach to the conceptual foundations of mathematics and the sciences. I introduce and motivate an IF first-order modal language endowed with a game-theoretic semantics of perfect information. The resulting interpretive independence-friendly logic (IIF) allows to formulate some basic model-theoretic notions that are inexpressible in the ordinary quantified modal logic. Moreover, I argue that some key concepts of Kripke’s new theory of reference are (...) adequately modeled within IIF. Finally, I compare the logic IIF to David Lewis' counterpart theory, drawing some morals concerning the interrelation between metaphysical and semantic issues in possible-world semantics. (shrink)

A claim by David K. Lewis (1986) that his counterpart theory provides a semantics for intensional languages is critiqued by showing that basic principles of modal logic fail to be valid in counterpart theory & by investigating problematic counterpart-theoretical translations of instances of universal instantiation. From Lewis's postulate that individuals inhabit only one world & have counterparts in other worlds, it follows that the relation between an object & its counterparts is nontransitive & nonsymmetric; consequently, an object does not need (...) to have exactly one counterpart in any world. The failure of modal principles in counterpart theory is ascribed to the possibility that an object has no counterpart in a given world, whereas universal instantiation becomes invalid when an object has more than one counterpart in a given world. 3 References. Adapted from the source document. (shrink)

It is common lore that standard, Kripke-style semantics for quantified modal logic is incompatible with the view that no individual may belong to more than one possible world, a view that seems to require a counterpart-theoretic semantics instead. Strictly speaking, however, this thought is wrong-headed. This note explains why.

An important motivation for believing in the modal realist’s ontology of other concrete possible worlds and their inhabitants is its theoretical utility, centrally the reduction of ordinary modal talk to counterpart theory as showcased by David Lewis’s 1968 translation scheme. In a recent paper Harold Noonan, following the lead of John Divers, argues that Lewis’s scheme is not strictly adequate by the modal realist’s own lights, and that nothing short of jettisoning de dicto contingency will help. In this paper, I (...) argue that this is a serious overreaction. First, I show that Noonan’s problem does not touch Lewis’s proposal, since his translation scheme is not even concerned with the relevant sentences. Thus, Noonan’s problem only points to a limit in scope. I then go on to propose a straightforward extension of the translation scheme that provides translations for the allegedly problematic sentences, but does so endangering neither adequacy nor de dicto contingency. (shrink)

Saul Kripke has made fundamental contributions to a variety of areas of logic, and his name is attached to a corresponding variety of objects and results. 1 For philosophers, by far the most important examples are ‘Kripke models’, which have been adopted as the standard type of models for modal and related non-classical logics. What follows is an elementary introduction to Kripke’s contributions in this area, intended to prepare the reader to tackle more formal treatments elsewhere.2 2. WHAT IS A (...) MODEL THEORY? Traditionally, a statement is regarded as logically valid if it is an instance of a logically valid form, where a form is regarded as logically valid if every instance is true. In modern logic, forms are represented by formulas involving letters and special symbols, and logicians seek therefore to define a notion of model and a notion of a formula’s truth in a model in such a way that every instance of a form will be true if and only if a formula representing that form is true in every model. Thus the unsurveyably vast range of instances can be replaced for purposes of logical evaluation by the range of models, which may be more tractable theoretically and perhaps practically. Consideration of the familiar case of classical sentential logic should make these ideas clear. Here a formula, say (p & q) ∨ ¬p ∨ ¬q, will be valid if for all statements P.. (shrink)