We describe a general method for verifying inequalities between real-valued expressions, especially the kinds of straightforward inferences that arise in interactive theorem proving. In contrast to approaches that aim to be complete with respect to a particular language or class of formulas, our method establishes claims that require heterogeneous forms of reasoning, relying on a Nelson-Oppen-style architecture in which special-purpose modules collaborate and share information. The framework is thus modular and extensible. A prototype implementation shows that the method is promising, (...) complementing techniques that are used by contemporary interactive provers. (shrink)

Theories of children's developing understanding of mind tend to emphasize either individualistic processes of theory formation, maturation, or introspection, or the process of enculturation. However, such theories must be able to account for the accumulating evidence of the role of social interaction in the development of social understanding. We propose an alternative account, according to which the development of children's social understanding occurs within triadic interaction involving the child's experience of the world as well as communicative interaction with others about (...) their experience and beliefs (Chapman 1991; 1999). It is through such triadic interaction that children gradually construct knowledge of the world as well as knowledge of other people. We contend that the extent and nature of the social interaction children experience will influence the development of children's social understanding. Increased opportunity to engage in cooperative social interaction and exposure to talk about mental states should facilitate the development of social understanding. We review evidence suggesting that children's understanding of mind develops gradually in the context of social interaction. Therefore, we need a theory of development in this area that accords a fundamental role to social interaction, yet does not assume that children simply adopt socially available knowledge but rather that children construct an understanding of mind within social interaction. Key Words: language; Piaget; social interaction; theories of mind; Vygotsky; Wittgenstein. (shrink)

Knobe's laudable conclusion that we make sense of our social world based on moral considerations requires a development account of human thought and a theoretical framework. We outline a view that such a moral framework must be rooted in social interaction.

Susan Hurley's shared circuits model (SCM) rightly begins in action and progresses through a series of layers; but it fails to reach action understanding because it relies on mirroring as a driving force, draws on heavily criticized theories, and neglects the need for shared experience in our grasp of social understanding.

The ability to take others’ perspectives on the self has important psychological implications. Yet the logically and developmentally prior question is how children develop the capacity to take others’ perspectives. We discuss the development of joint attention in infancy as a rudimentary form of perspective taking and critique examples of biological and individualistic approaches to the development of joint attention. As an alternative, we present an activity-based relational perspective according to which infants develop the capacity to coordinate attention with others (...) by differentiating the perspectives of self and other from shared activity. Joint attention is then closely related to language development, which makes further social development possible. We argue that the ability to take the perspective of others on the self gives rise to the possibility of language, rationality and culture. (shrink)

The ability to take others’ perspectives on the self has important psychological implications. Yet the logically and developmentally prior question is how children develop the capacity to take others’ perspectives. We discuss the development of joint attention in infancy as a rudimentary form of perspective taking and critique examples of biological and individualistic approaches to the development of joint attention. As an alternative, we present an activity-based relational perspective according to which infants develop the capacity to coordinate attention with others (...) by differentiating the perspectives of self and other from shared activity. Joint attention is then closely related to language development, which makes further social development possible. We argue that the ability to take the perspective of others on the self gives rise to the possibility of language, rationality and culture. (shrink)

We explore three types of criticisms of our theory on the development of children's social understanding. We reject suggestions that we offer nothing new to traditional theories of development or recent “social” accounts of “theory of mind.” Second, we take the point that there are grounds for improving our account of dyadic interaction in infancy but reject claims that we have not sufficiently accounted for how we incorporate the notions of criteria and structure into the theory. Third, we accept that (...) the epistemic triangle, as defined, would benefit from an affective dimension and such a formulation could be used to describe the dynamic of developmental change from infancy to beyond early childhood. We still feel that the combination of Wittgenstein, Vygotsky, and Piaget remains as an antidote to the flaws in current “theories of mind” approaches to social understanding. (shrink)

In place of Tomasello's explanation for the source of moral obligation, we suggest that it develops from the concern for others already implicit in the human developmental system. Mutual affection and caring make the development of communication and thinking possible. Humans develop as persons within such relationships and this develops into respect and moral obligation.

Carruthers presents an interesting analysis of confabulation and a clear attack on introspection. Yet his theory-based alternative is a mechanistic view of which neglects the fact that social understanding occurs within a network of social relationships. In particular, the role of language in his model is too simple.

The violation of the Bell inequality means that measurement-results in the two wings of the experiment cannot be screened off from one another, in the sense of Reichenbach. But does this mean that there is causation between the results? I argue that it does, according to Lewis's counterfactual analysis of causation and his associated views. The reason lies in his doctrine that chances evolve by conditionalization on intervening history. This doctrine collapses the distinction between the conditional probabilities that are (...) used to state screening off, and the counterfactuals with chance consequents that are used to state lack of causation. I briefly discuss ways to evade my argument. (shrink)

I reject Norton and Earman's hole argument that spacetime substantivalism is incompatible with determinism. I reconcile these both technically and philosophically. There is a technical definition of determinism that is not violated by pairs of models of the kind used in the hole argument. And technicalities aside, the basic idea of determinism is not violated if we claim that at most one of the two models represents a possible world. This claim can be justified either by metrical essentialism, or by (...) denying transworld identity for points: I prefer the latter. (shrink)

This paper forms part of a wider campaign: to deny pointillisme, the doctrine that a physical theory's fundamental quantities are defined at points of space or of spacetime, and represent intrinsic properties of such points or point-sized objects located there; so that properties of spatial or spatiotemporal regions and their material contents are determined by the point-by-point facts. More specifically, this paper argues against pointillisme about the concept of velocity in classical mechanics; especially against proposals by Tooley, Robinson and (...) class='Hi'>Lewis. A companion paper argues against pointillisme about -geometry, as proposed by Bricker. To avoid technicalities, I conduct the argument almost entirely in the context of "Newtonian" ideas about space and time, and the classical mechanics of point-particles, i.e. extensionless particles moving in a void. But both the debate and my arguments carry over to relativistic physics. Introduction The wider campaign 2.1 Connecting physics and metaphysics 2.1.1 Avoiding controversy about the intrinsic–extrinsic distinction 2.1.2 Distinction from three mathematical distinctions 2.2 Classical mechanics is not pointilliste, and can be perdurantist 2.2.1 Two versions of pointillisme 2.2.2 Two common claims 2.2.3 My contrary claims 2.3 In more detail... 2.3.1 Four violations of pointillisme 2.3.2 For perdurantism Velocity as intrinsic? 3.1 Can properties represented by vectors be intrinsic to a point? 3.2 Orthodox velocity is extrinsic but local 3.2.1 A question and a debate 3.2.2 The verdict 3.3 Against intrinsic velocity 3.3.1 A common view—and a common problem 3.3.2 Tooley's proposal and his arguments 3.3.3 Tooley's further discussion "Shadow velocities": Lewis and Robinson 4.1 The proposal 4.2 Criticism: the vector field remains unspecified 4.3 Avoiding the presupposition of persistence, using Hilbert's symbol 4.4 Comparison with Robinson and Lewis. (shrink)

I compare deterministic and stochastic hidden variable models of the Bell experiment, exphasising philosophical distinctions between the various ways of combining conditionals and probabilities. I make four main claims. (1) Under natural assumptions, locality as it occurs in these models is equivalent to causal independence, as analysed (in the spirit of Lewis) in terms of probabilities and conditionals. (2) Stochastic models are indeed more general than deterministic ones. (3) For factorizable stochastic models, relativity's lack of superluminal causation does not (...) favour locality over completeness. (4) If we prohibit all superluminal causation, then the violation of the Bell inequality teaches us a lesson, besides quantum mechanics' familiar ones that quantities can lack precise values and that pairs of quantities can lack joint probabilities: namely, some pairs of events are not screened off by their common past. (shrink)

This paper discusses some of the modal involvements of analytical mechanics. I first review the elementary aspects of the Lagrangian, Hamiltonian and Hamilton-Jacobi approaches. I then discuss two modal involvements; both are related to David Lewis' work on modality, especially on counterfactuals. The first is the way Hamilton-Jacobi theory uses ensembles, i.e. sets of possible initial conditions. The structure of this set of ensembles remains to be explored by philosophers. The second is the way the Lagrangian and Hamiltonian approaches' (...) variational principles state the law of motion by mentioning contralegal dynamical evolutions. This threatens to contravene the principle that any actual truth, in particular an actual law, is made true by actual facts. Though this threat can be avoided, at least for simple mechanical systems, it repays scrutiny; not least because it leads to some open questions. (shrink)

This is the first of four papers prompted by a recent literature about a doctrine dubbed spacetime functionalism. This paper gives our general framework for discussing functionalism. Following Lewis, we take it as a species of reduction. We start by expounding reduction in a broadly Nagelian sense. Then we argue that Lewis’ functionalism is an improvement on Nagelian reduction.This paper sets the scene for the other papers, which will apply our framework to theories of space and time. (So (...) those papers address the space and time literature: both recent and older, and physical as well as philosophical literature. But the four papers can be read independently.)Overall, we come to praise spacetime functionalism, not to bury it. But we criticize the recent philosophical literature for failing to stress: functionalism’s being a species of reduction (in particular: reduction of chrono-geometry to the physics of matter and radiation);functionalism’s idea, not just of specifying a concept by its functional role, but of specifying several concepts simultaneously by their roles;functionalism’s providing bridge laws that are mandatory, not optional: they are statements of identity (or co-extension) that are conclusions of a deductive argument, rather than contingent guesses or verbal stipulations; and once we infer them, we have a reduction in a Nagelian sense.On the other hand, some of the older philosophical literature, and the mathematical physics literature, is faithful to these ideas (i) to (iii)—as are Torretti’s writings. (But of course, the word ‘functionalism’ is not used; and themes like simultaneous unique definition are not articulated.) Thus in various papers, falling under various research programmes, the unique definability of a chrono-geometric concept (or concepts) in terms of matter and radiation, and a corresponding bridge law and reduction, is secured by a precise theorem. Hence our desire to celebrate these results as rigorous renditions of spacetime functionalism. (shrink)

I show that locality, as it occurs in EPR arguments for the incompleteness of quantum mechanics, can be construed as causal independence understood in terms of Lewis' counterfactual analysis of causation. This construal has two benefits. It supplements recent analyses, which have not treated locality in detail. And it clarifies the relation between two EPR arguments that have recently been distinguished. It shows that the simpler of the two is more complex than has been thought; and that the other (...) argument does not need 'counterfactual definiteness'. (shrink)

Some recent philosophical debate about persistence has focussed on an argument against perdurantism that discusses rotating perfectly homogeneous discs. The argument has been mostly discussed by metaphysicians, though it appeals to ideas from classical mechanics, especially about rotation. In contrast, I assess the RDA from the perspective of the philosophy of physics. After introducing the argument and emphasizing the relevance of physics, I review some metaphysicians' replies to the argument, especially those by Callender, Lewis, Robinson and Sider. Thereafter, I (...) argue for three main conclusions. They all arise from the fact, emphasized in Section 2, that classical mechanics is both more subtle, and more problematic, than philosophers generally realize. The first conclusion is that the RDA can be formulated more strongly than is usually recognized: it is not necessary to ``imagine away'' the dynamical effects of rotation. The second is that in general relativity, the RDA fails because of frame-dragging. The third is that even setting aside general relativity, the strong formulation of the RDA can after all be defeated. Namely, by the perdurantist taking objects in classical mechanics to have only temporally extended, i.e. non-instantaneous, temporal parts: which immediately blocks the RDA. Admittedly, this version of perdurantism defines persistence in a weaker sense of `definition' than pointilliste versions that aim to define persistence assuming only instantaneous temporal parts. But I argue that temporally extended temporal parts: can do the jobs within the endurantism- perdurantism debate that the perdurantist wants temporal parts to do; and are supported by both classical and quantum mechanics. (shrink)

I commemorate David Lewis by discussing an aspect of modality within analytical mechanics, which is closely related to his work on counterfactuals. This concerns the way Hamilton ‐Jacobi theory uses ensembles, i.e. sets of possible initial conditions.

I present aspects of causal set theory (a research programme in quantum gravity) as being en route to achieving a reduction of Lorentzian geometry to causal sets. I take reduction in philosophers' sense; and I argue that the prospects are good for there being a reduction of the type envisaged by Nagel. (I also discuss the prospects for the stronger functionalist variant of Nagelian reduction, that was formulated by Lewis.) One main theme will be causal set theory's use of (...) a physical scale (viz. the Planck scale) to formulate how it recovers a Lorentzian manifold. This use illustrates various philosophical topics relevant to reduction, such as limiting relations between theories, and the role of analogy. I also emphasise causal set theory's probabilistic method, viz. Poisson sprinkling: which is used both for formulating the reduction and for exploring its prospects. (shrink)

Deterministic physical theories are not beyond the reach of scientific discovery. From this fact I show that David Lewis was mistaken to think that small counterfactual perturbations from deterministic worlds involve violations of those world’s laws.

This paper forms part of a wider campaign: to deny pointillisme. That is the doctrine that a physical theory's fundamental quantities are defined at points of space or of spacetime, and represent intrinsic properties of such points or point-sized objects located there; so that properties of spatial or spatiotemporal regions and their material contents are determined by the point-by-point facts. More specifically, this paper argues against pointillisme about the structure of space and-or spacetime itself, especially a paper by Bricker (1993). (...) A companion paper argues against pointillisme in mechanics, especially about velocity; it focusses on Tooley, Robinson and Lewis. To avoid technicalities, I conduct the argument almost entirely in the context of ``Newtonian'' ideas about space and time. But both the debate and my arguments carry over to relativistic, and even quantum, physics. (shrink)

While Plato recommended expelling poets from the ideal society, W. H. Auden famously declared that poetry makes nothing happen. The 19 contributions to the present book avoid such polarized views and, responding in different ways to the “ethical turn” in narrative theory, explore the varied ways in which narratives encourage readers to ponder matters of right and wrong. All work from the premise that the analysis of narrative ethics needs to be linked to a sensitivity to esthetic form. The ethical (...) issues are accordingly located on different levels. Some are clearly presented as thematic concerns within the text considered, while others emerge through the presentation of character and event by means of particular narrative techniques. The objects of analysis include such well-known or canonical texts as Biblical Old Testament stories, Mark Twain’s Huckleberry Finn, J. R. R. Tolkien’s The Lord of the Rings, Vladimir Nabokov’s Lolita, Jonathan Littell’s The Kindly Ones, Ann Radcliffe’s The Italian and Matthew Lewis’s The Monk. Others concentrate on less-well-known texts written in languages other than English. There are also contributions that investigate theoretical issues in relation to a range of different examples. (shrink)

I show that locality, as it occurs in EPR arguments for the incompleteness of quantum mechanics, can be construed as causal independence understood in terms of Lewis’ counterfactual analysis of causation. This construal has two benefits. It supplements recent analyses, which have not treated locality in detail. And it clarifies the relation between two EPR arguments that have recently been distinguished. It shows that the simpler of the two is more complex than has been thought; and that the other (...) argument does not need ‘counterfactual definiteness’.I aim to show that in the EPR argument (Einstein et al. 1935) for the incompleteness of quantum mechanics (QM), locality can be taken as causal independence, understood in terms of Lewis’ counterfactual analysis of causation.Recent analyses of the EPR argument makes this construal of locality timely, for two reasons. First, these analyses typically say little about locality. (shrink)

ABSTRACTThe ubiquity of digital communication channels such as social media platforms, video sites, and mobile apps has transformed the relational experience between audiences and brand entities. Whether engaging within a consumer goods market, a professional services industry, or a news and infotainment source, audiences and brand entities have inhabited a new ecosystem that has challenged the acceptance of the classic purchase funnel model pioneered by Elias St. Elmo Lewis. This article reviews the conception of a postpurchase funnel media environment (...) and seeks to moralize its transaction-driven expediency in 3 ways. First, it explores the legitimacy of an audience-centric ecosystem as a theoretical substitute for the purchase funnel model. Second, it introduces MacIntyre’s concept of virtue ethics as a grounding moral philosophy in the postpurchase funnel environment. Finally, it reviews two cases of postpurchase funnel marketing abuses and recommends strategies that commit brand entities to a bilatera... (shrink)

Some recent epistemologists propose that certainty is the norm of action and assertion. This proposal is subject to skeptical worries. If, as is usually supposed, certainty is very hard to come by, legitimate action and assertion will be rare. To remedy this, some have conjoined their certainty-norms with a context-sensitive semantics for ‘certainty’. For a proposition to be certain for you, you only need to be able to exclude relevant alternatives. I argue that, depending on what makes an alternative relevant, (...) this kind of view is disingenuous. In particular, if an alternative can be made relevant by being relevant to rational action, it allows an escape from the skeptical consequences only by licensing David Lewis-style utterances of the form, “You know that p only if there is no probability, no matter how small, that not-p—Psst!—Unless that probability is really small.” While there are legitimate ways to exclude some possibilities from relevance, it is disingenuous, I argue, to exclude possibilities from relevance on the basis of the very characteristic—low but nonzero probability—that is claimed to be incompatible with certainty. (shrink)

The prevailing notion that the problem of essential indexicals must be solved through the theory of meaning of attitude ascriptions is incorrect. Well-known attempts to solve the problem along those lines, e.g., the proposals of Lewis and Perry , have rested on the overly optimistic assumption that there is no limit in principle to the access one may have to the contents of someone else’s thoughts, including their knowledge. That assumption is challenged in this essay. The hazards associated with (...) limited accessibility can be and indeed must be alleviated by an epistemological theory in such a way that allows for a new nonsemantic approach to the problem. The following is an outline of the arguments in favor of this approach. In the first part, the problem of essential indexicals and the familiar corollary thesis that such indexicals are not reducible to nonindexicals is briefly reviewed. In the second part, indexical irreducibility is shown to hold for a range of explanations of theoretical rationality in addition to the basic explanations of action in which the irreducibility is typically illustrated. (shrink)

The path of those who would approach the study of Bentham's writings on Evidence has been considerably smoothed by the recent publication of William Twining's work on the evidence theories of Bentham and Wigmore. The material on evidence is now being tackled by the Bentham Project. It presents no easy task. The central core, The Rationale of Judicial Evidence, edited and published by John Stuart Mill in 1827, exists only in the printed version, the MSS from which Mill worked having (...) disappeared. But a substantial body of related material which survives has yet to be thoroughly investigated, though William Twining has made a gallant start. A new edition of the work hitherto known as ‘An Introductory View of the Rationale of Evidence’, first printed in full in the Bowring edition of the Works of Jeremy Bentham is in preparation. The first fruits of this endeavour is that the title of that work as it should appear in due course in the new Collected Works will be Introduction to the Rationale of Evidence: An Introductory View for the Use of Lawyers as well as Non-lawyers, the title in fact given to the work by Bentham. It is intended that what follows should similarly be of use to non-lawyers as well as lawyers. (shrink)

This paper asks how we should regard the laws and customs of armed conflict, and specifically the rule prohibiting the targeting of civilians. What view should we take of the moral character and significance of such rules? Some philosophers have suggested that they are best regarded as useful conventions. This view is sometimes motivated by a "deep moral critique" of the rule protecting civilians: Jeff McMahan believes for example that the existing rules protect some who ought to be liable to (...) attack (on account of their having voluntarily contributed to the injustice or aggression being resisted). He thinks we would be better off with a different principle of discrimination in warfare. But McMahan acknowledges that for the time being we must stick with the rules that we have. The present paper does five things: (1) it explores and takes further some of McMahan's insights about the importance of existing positive law in this area; (2) it argues that some of the features that philosophers find problematic with the rule offering blanket protection to all civilians have to do with administrability; (3) it raises some questions about whether the rule protecting civilians can really be regarded as a convention (and it argues that certainly it cannot be regarded as a "Lewis-convention" in a strict sense); (4) to the extent that the rule can be regarded as conventional, the paper argues that it remains a deadly serious moral rule, partly because of the circumstances of death and destruction in which it operates and which it tries to ameliorate, and partly on account of its fragility. The fifth point is the most important. (5) The rule protecting civilians does not operate in circumstances in which, apart form positive law, civilians like everyone would be liable to attack. The rule operates against a moral background in which all deliberate killing is to be regarded as murder; some deliberate killings (of combatants) are privileged in warfare; but the rule about civilians reflects the fact that this is a strictly limited privilege and that those who target civilians do not get the benefit of it. Changing our view of the default position in this way enables us to better understand the distinctive work that this rule does. (shrink)

give a proof of the existence of nonlocal influences acting on correlated spin-1/2 particles in the singlet state which does not require any particular interpretation of quantum mechanics (QM). (Except Stapp holds that the proof fails under a many-worlds interpretation of QM—a claim we analyse in 1.2.) Recently, in responding to Redhead's ([1987], pp. 90-6) criticism that the Stapp 1 proof fails under an indeterministic interpretation of QM, Stapp [1989] (henceforth Stapp 2), has revised the logical structure of his proof (...) including its crucial locality assumption. Our main aim is to show that this revision is a step in the wrong direction because it faces two difficulties which undermine the resulting proof's significance (3.1) and validity (3. 2). We also clarify and extend the Stapp 1 proof (1. 1) with the aid of Lewis' analysis of counterfactuals (1. 2) and causal dependence (2. 2 and 2. 3). In so doing, we are able to identify two new defects in the Stapp 1 proof (1. 3 and 2. 1) in addition to corroborating Redhead's criticism (2. 2). Also, the additional assumptions which save the Stapp 1 proof's validity are detailed (2. 3) and some new difficulties for the determinist are pointed out by exploiting a slightly extended version of the proof (2. 4). In providing this full analysis of the Stapp 1 proof, we also construct the necessary framework within which to provide a critique of Stapp 2's proof (3). *Portions of this paper were presented by R. K. Clifton to the 1988 British Society for the Philosophy of Science Conference at the University of Southampton. R. K. Clifton wishes to thank the Natural Sciences and Engineering Research Council of Canada, the Royal Commission for the Exhibition of 1851, and the Governing Body of Peterhouse at Cambridge University for support during this work. (shrink)

We review three broadly geometrodynamical---and in part, Machian or relational---projects, from the perspective of spacetime functionalism. We show how all three are examples of functionalist reduction of the type that was advocated by D. Lewis, and nowadays goes by the label `the Canberra Plan’. The projects are: the recovery of geometrodynamics by Hojman et al. ; the programme of Schuller and collaborators to deduce a metric from the physics of matter fields; the deduction of the ADM Hamiltonian by Gomes (...) and Shyam. We end by drawing a positive corollary about shape dynamics: namely, it has a good rationale for the Hamiltonian it postulates. (shrink)

v. 1. Essays on ethics by the Earl of Shaftesbury, Frances Hutcheson ; Samuel Butler ; Adam Smith ; Jeremy Bentham - v. 2. Essays by Samuel Clarke ; John Balguy ; Richard Price ; John Brown ; John Clarke ; Ralph Cudworth ; John Gay ; Thomas Hobbes ; Henry Home Kames ; John Locke ; John Mandeville ; William Paley ; William Wollaston.

Are morals subjective? -- Ancient moral thinkers -- Socrates (469-399 bce) -- Aristotle (384-322 bce) -- Epicurus (342-270 bce) -- Epictetus (55-135 ce) -- Modern moral thinkers -- Desiderius Erasmus (1466-1536) -- Michel de Montaigne (1533-1592) -- Baruch de Spinoza (1632-1677) -- David Hume (1711-1776) -- Adam Smith (1723-1790) -- Immanuel Kant (1724-1804) -- Edward Gibbon (1737-1794) -- Jeremy Bentham (1748-1832).

We discuss from a philosophical perspective the way in which the normal concept of time might be said to `emerge' in a quantum theory of gravity. After an introduction, we briefly discuss the notion of emergence, without regard to time. We then introduce the search for a quantum theory of gravity ; and review some general interpretative issues about space, time and matter. We then discuss the emergence of time in simple quantum geometrodynamics, and in the Euclidean approach. Section 6 (...) concludes. (shrink)

This book is a defense of modal realism; the thesis that our world is but one of a plurality of worlds, and that the individuals that inhabit our world are only a few out of all the inhabitants of all the worlds. Lewis argues that the philosophical utility of modal realism is a good reason for believing that it is true.

Letter responding to "An Office on Main Street: Health Care Dilemmas in Small Communities," HCR, July-August 1999.

The intellectual history of the last quarter of this century has been marked by the growing influence of Africana thought--an area of philosophy that focuses on issues raised by the struggle over ideas in African cultures and their hybrid forms in Europe, the Americas, and the Caribbean. Existentia Africana is an engaging and highly readable introduction to the field of Africana philosophy and will help to define this rapidly growing field. Lewis R. Gordon clearly explains Africana existential thought to (...) a general audience, covering a wide range of both classic and contemporary thinkers--from Douglass and DuBois to Fanon, Davis and Zack. (shrink)

David Lewis (1941-2001) was Class of 1943 University Professor of Philosophy at Princeton University. His contributions spanned philosophical logic, philosophy of language, philosophy of mind, philosophy of science, metaphysics, and epistemology. In On the Plurality of Worlds, he defended his challenging metaphysical position, "modal realism." He was also the author of the books Convention, Counterfactuals, Parts of Classes, and several volumes of collected papers.