The interpretation of Lewis?s doctrine of natural properties is difficult and controversial, especially when it comes to the bearers of natural properties. According to the prevailing reading ? the minimalist view ? perfectly natural properties pertain to the micro-physical realm and are instantiated by entities without proper parts or point-like. This paper argues that there are reasons internal to a broadly Lewisian kind of metaphysics to think that the minimalist view is fundamentally flawed and that a liberal view, according to (...) which natural properties are instantiated at several or even at all levels of reality, should be preferred. Our argument proceeds by reviewing those core principles of Lewis?s metaphysics that are most likely to constrain the size of the bearers of natural properties: the principle of Humean supervenience, the principle of recombination in modal realism, the hypothesis of gunk, and the thesis of composition as identity. (shrink)

David Lewis's book 'On the Plurality of Worlds' mounts an extended defense of the thesis of modal realism, that the world we inhabit the entire cosmos of which we are a part is but one of a vast plurality of worlds, or cosmoi, all causally and spatiotemporally isolated from one another. The purpose of this article is to provide an accessible summary of the main positions and arguments in Lewis's book.

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. (A companion paper discusses other aspects of modality in analytical mechanics that are equally related to Lewis's work.).

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)

David Lewis claims that a simple sort of anti-Humeanism-that the rational agent desires something to the extent he believes it to be good-can be given a decision-theoretic formulation, which Lewis calls 'Desire as Belief' (DAB). Given the (widely held) assumption that Jeffrey conditionalising is a rationally permissible way to change one's mind in the face of new evidence, Lewis proves that DAB leads to absurdity. Thus, according to Lewis, the simple form of anti-Humeanism stands refuted. In this paper we investigate (...) whether Lewis's case against DAB can be strengthened by examining how it fares under rival versions of decision theory, including other conceptions of rational ways to change one's mind. We argue that the anti-Humean may escape Lewis's argument either by adopting a version of causal decision theory, or by claiming that the refutation only applies to hyper-idealised rational agents, or by denying that the decision-theoretic framework has the expressive capacity to formulate anti-Humeanism. (shrink)

In “Mathematics is megethology,” Lewis reconstructs set theory using mereology and plural quantification (MPQ). In his recontruction he assumes from the beginning that there is an infinite plurality of atoms, whose size is equivalent to that of the set theoretical universe. Since this assumption is far beyond the basic axioms of mereology, it might seem that MPQ do not play any role in order to guarantee the existence of a large infinity of objects. However, we intend to demonstrate that mereology (...) and plural quantification are, in some ways, particularly relevant to a certain conception of the infinite. More precisely, though the principles of mereology and plural quantification do not guarantee the existence of an infinite number of objects, nevertheless, once the existence of any infinite object is admitted, they are able to assure the existence of an uncountable infinity of objects. So, if—as Lewis maintains—MPQ were parts of logic, the implausible consequence would follow that, given a countable infinity of individuals, logic would be able to guarantee an uncountable infinity of objects. (shrink)

David Lewis is widely credited with the first formulation of common knowledge and the first rigorous analysis of convention. However, common knowledge and convention entered mainstream game theory only when they were formulated, later and independently, by other theorists. As a result, some of the most distinctive and valuable features of Lewis' game theory have been overlooked. We re-examine this theory by reconstructing key parts in a more formal way, extending it, and showing how it differs from more recent game (...) theory. In contrast to current theories of common knowledge, Lewis' theory is based on an explicit analysis of the modes of reasoning that are accessible to rational individuals and so can be used to analyse the genesis of common knowledge. Lewis' analysis of convention emphasises the role of inductive reasoning and of salience in the maintenance of conventions over time. Footnotes Earlier versions of this paper were presented at the 13th Amsterdam Colloquium at the University of Amsterdam, at a workshop on social norms at Wissenschaftskolleg zu Berlin, and at seminars at Tilburg University and the University of Bristol. We are grateful for comments from participants at those meetings, from two anonymous referees, and from Michael Bacharach, Nick Bardsley, Cristina Bicchieri, Luc Bovens, Simon Grant, David McCarthy, Shepley Orr, Brian Skyrms, Peter Vanderschraaf, Peter Wakker and Jörgen Weibull. Robert Sugden's work was supported by the Leverhulme Trust. (shrink)

This paper considers two aspects of Lewis's metaphysics to which spatiotemporal relations appear central, with the aim of showing them to be less so. First, Lewis reluctantly characterises what it is for two things to be part of the same possible world in terms of an analogically spatiotemporal category of relations, rather than a wider natural external category. But Lewis's reason for restricting himself to the narrower category is unpersuasive. Second, Humean supervenience is formulated with spatiotemporal relations (...) at its core. But that seems negotiable. A reason for caring about this is that quantum mechanics is supposed to threaten Lewis's metaphysics by introducing natural external relations that are not (even analogically) spatiotemporal, hence the interest in how central spatiotemporal relations really are. (shrink)

According to Lewis's modal realism, all ways the world could be are represented by possible worlds, and all possible worlds represent some way the world could be. That there are just the right possible worlds to represent all and only the ways the world could be is to be guaranteed by the principle of recombination. Lewis sketches the principle (put roughly: anything can co-exist with anything else), but does not spell out a precise version that generates just the right possibilities. (...) David Efird and Tom Stoneham have offered a principle that aims to do just that.In this paper, we argue that Efird's and Stoneham's principle of recombination is not successful – it fails to generate the right possibilities – but we also suggest ways that their account might be improved to solve the problem we raise. We also argue against Efird's and Stoneham's claim that the correct principle of recombination demonstrates the possibility of nothing concrete – it is true that their principle of recombination has models consistent with the existence of an empty world, but we only get the possibility of nothing if mereologically null individuals are possible. The Lewisian should only think mereologically null individuals are possible if he or she has some independent reason for believing in the possibility of an empty world, so the principle of recombination provides no new evidence for that possibility. We draw some morals from this for the correct way to formulate the principle of recombination. (shrink)

Problems about the accidental properties of properties motivate us--force us, I think--not to identify properties with the sets of their instances. If we identify them instead with functions from worlds to extensions, we get a theory of properties that is neutral with respect to disputes over counterpart theory, and we avoid a problem for Lewis's theory of events. Similar problems about the temporary properties of properties motivate us--though this time they probably don't force us--to give up this theory as well, (...) and to identify properties with functions from world, time pairs to extensions. Again, the replacement theory is neutral with respect to a metaphysical dispute that the old theory (arguably) forces us to take a stand on--the dispute over whether objects have temporal parts. It also allows us to give a smoother semantics for predication, to better accommodate our intuitions about which objects temporary properties are properties of, and to make temporally self-locating beliefs genuinely self -locating. (shrink)

David Lewis was one of the most important philosophers of the 20th century working in the Anglo-American analytic tradition. His corpus is extraordinary for its breadth of subject matter and for its systematicity. For both these reasons, it is difficult to do justice to his work in a short space—there are rich interconnections among his myriad writings, and numerous possible entry points. This article approaches Lewis and his work in three passes: first, a biographical tracing of his intellectual influences; second, (...) a summary of his metaphilosophy; third, a survey of his more specific philosophical views, mostly following their order of conceptual dependence. (shrink)

Infinite time Turing machines extend the operation of ordinary Turing machines into transfinite ordinal time. By doing so, they provide a natural model of infinitary computability, a theoretical setting for the analysis of the power and limitations of supertask algorithms.

There are two parts to Lewis's account of the de se. First there is the idea that the objects of de se thought (and, by extension of de dicto thought too) are properties, not propositions. This is the idea that is center-stage in Lewis's discussion. Second there is the idea that the relation that thinkers bear to these properties is that of self-ascription. It is crucial to LewisÕs account that this is understood as a fundamental, unanalyzable, notion: self-ascription of a (...) property is not ascription of a property to the self, on a par with ascription to someone else. This has been overlooked in much recent discussion, especially when Lewis's account is understood in terms of centered worlds. When it is back in focus it brings problems. An almost Cartesian starting point is required; and first-person plural ascriptions, and those with first person pronouns other than in subject position, become unmanageably complex. (shrink)

Lewis never saw philosophy of language as foundational in the way that many have. One of the most distinctive features of his work is the robust confidence that questions in metaphysics or mind can be addressed head on, and not through the lens of language.

David Lewis's untimely death on 14 October 2001 deprived the philosophical community of one of the outstanding philosophers of the 20th century. As many obituaries remarked, Lewis has an undeniable place in the history of analytical philosophy. His work defines much of the current agenda in metaphysics, philosophical logic, and the philosophy of mind and language. This volume, an expanded edition of a special issue of the Australasian Journal of Philosophy, covers many of the topics for which Lewis was well (...) known, including possible worlds, counterpart theory, vagueness, knowledge, probability, essence, fiction, laws, conditionals, desire and belief, and truth. Many of the papers are by very established philosophers; others are by younger scholars including many he taught. The volume also includes Lewis's Jack Smart Lecture at the Australian National University, "How Many Lives has Schrodinger's Cat?," published here for the first time. Lewisian Themes will be an invaluable resource for anyone studying Lewis's work and a major contribution to the many topics that he mastered. (shrink)

Finkish dispositions, those dispositions that are lost when their conditions of realization occur, pose deep problems for counterfactual accounts of dispositions. David Lewis has argued that the counterfactual approach can be rescued, offering such an account that purports to handle finkish as well as other dispositions. The paper argues that Lewis's account fails to account for several kinds of dispositions, one of which involves failure to distinguish parallel processes from unitary processes.