Theodore Sider

While many are impressed with the utility of possible worlds in linguistics and philosophy, few can accept the modal realism of David Lewis, who regards possible worlds as sui generis entities of a kind with the concrete world we inhabit.1 Not all uses of possible worlds require exotic ontology. Consider, for instance, the use of Kripke models to establish formal results in modal logic. These models contain sets often regarded for heuristic reasons as sets of “possible worlds”. But the “worlds” in these sets can be anything at all; they can be numbers, or people, or sh. The set of worlds, together with the accessibility relation and the rest of the model, is used as a purely formal structure.2 One can even go beyond establishing results about formal systems and apply Kripke models to English, as Charles Chihara has recently argued.3 Chihara shows, for instance, how to use Kripke models (plus primitive modal notions) to give an account of validity for English modal sentences. In other cases worlds are not really needed at all. It is often vivid to give a counterexample thus: “There is a possible world in which P. Since your theory implies that in all worlds, not-P, your theory is wrong.” But the counterexample could just as easily be given using modal operators: “Possibly, P. Since your theory implies that it is necessary that not-P, your theory is wrong.”.

The intimate relationship between X and Y consists in the existence of (metaphysically) necessary truths correlating their occurrences/existences/instantiations. E would be in some sense “overdetermined” if caused by both X and Y.2 Some philosophers say this would be bad, that this cannot or does not happen, that we should construct theories ruling it out, at least in certain cases.3 But why? Given the necessary truths correlating objects and their parts, objects and events concerning those objects, physical and supervenient mental properties, and so on, X and Y do both seem to be causes of E. Should we say that a baseball..

Locke’s view that continuants are numerically distinct from their constituting hunks of matter is popular enough to be called the “standard account”.1 It was given its definitive contemporary statement by David Wiggins in Sameness and Substance2, and has been defended by many since. Baker’s interesting book contributes new arguments for this view, a new definition of ‘constitution’, and a sustained application to persons and human animals. Much of what she says develops this view in new and important ways. But in some cases she does not advance the position, and in others she takes steps backwards. According to Baker, a person is numerically distinct from her constituting animal. One of Baker’s leading arguments is surprisingly unconvincing. Persons differ in important ways from non-human animals. Only persons are moral agents, modify their goals, have wars, culture, etc. If persons were identical to animals—if we were “nothing but animals”, as she puts it—then the manifest discontinuity between humans and non-human animals would be located “within the domain of biology”. “But from a biological point of view, human animals…are biologically continuous with non-human animals.” (p. 17) The argument fails: why should identifying persons with animals preclude saying that these particular animals have radically distinctive features that are of little interest to biologists? The traditional case for non-identity (which Baker accepts) is more powerful: a person and her constituting animal differ by having different persistence conditions. If my memories were transferred to a new body and my old body destroyed, I the person might survive, but the human animal who constituted me would perish. Therefore, before the transfer, I and the animal that constituted me would be numerically distinct but extremely similar things located in exactly the same place. This consequence—the central thesis of the Wiggins view—is surprising: so surprising that some reject the Wiggins view on that basis..

Think of “locations” very abstractly, as positions in a space, any space. Temporal locations are positions in time; spatial locations are positions in (physical) space; particulars are locations in quality space. Should we reify locations? Are locations entities? Spatiotemporal relation- alists say there are no such things as spatiotemporal locations; the fundamental spatial and temporal facts involve no locations as objects, only the instantiation of spatial and temporal relations. The denial of locations in quality space is the bundle theory, according to which particulars do not exist; facts apparently about particulars really concern relations between universals. A “space”, in our abstract sense, consists of a set of objects, together with properties and relations defined on those objects. The objects are the locations of the space, and the distribution of the properties and relations over the locations defines the space’s structure. All spaces are thus quality spaces; when the relations are thought of as spatiotemporal then the space is also a spatiotemporal space. By not reifying locations one denies that these abstract spaces isomorphically represent the real world. The real world does in some sense have a structure that can be non-isomorphically represented by a space (or, more likely, a class of spaces), but the locations in those spaces do not correspond to anything real. We will examine modal considerations on reifying locations. Denying the existence of spatiotemporal locations excludes certain possibilities for spatiotemporal reality. Denying the existence of qualitative locations excludes certain possibilities for qualitative space. In each case the excluded possibilities are pre-analytically possible. Some of the possibilities can be reinstated by modifying the locationless theories, but at the cost of an unattractive holism. Do these modal considerations mandate postulating locations? That depends on whether modal intuition can teach us about the actual world..

Eli Hirsch has argued in many places that non-commonsensical ontological claims just couldn't be true, since there is strong metasemantic pressure to charitably interpret natural language---correct interpretations must, unless all else is highly unequal, count a sentence (especially a perceptual sentence) as true if ordinary speakers regard it as being obviously true. In previous work I replied that ontologists can stipulatively introduce a new language, "Ontologese", that is exempt from this pressure toward charity. Hirsch has recently objected to this proposal; this paper is my reply.

I defend counterpart theory against post-Kripkean objections. Trenton Merricks objects that no construction of ersatz counterparts is uniquely and intrinsically suitable; I reply that metaphysical constructions need not have these features. Sarah Moss refutes my solution (from "All the world's a stage") to the problem of timeless counting for temporal counterpart theory; I offer a new solution. Hazen, Fara, Williamson, and others have objected that counterpart theory generates an unacceptable logic for an actuality operator; I attempt to give a better semantics.

André Gallois’s Occasions of Identity injects a refreshing new perspective into an old debate. Actually, what is new is the advocacy of the perspective: Gallois takes up a view that many consider a non-starter, and shows this reaction to be premature. The debate is over the right way to understand the traditional puzzles involving two things being in the same place at the same time; the perspective is that identity can hold temporarily. Suppose an amoeba, name it AMOEBA, divides in two. One of the resultant amoebas, POND, lives in a pond; the other, SLIDE, is examined on a slide in a laboratory. Does AMOEBA survive this process, and if so, does it survive as POND or SLIDE? If we stipulate that POND and SLIDE are symmetrically related to AMOEBA then it seems arbitrary to identify AMOEBA with exactly one of POND and SLIDE. But we cannot identify AMOEBA with each, for then by the transitivity and symmetry of identity we would wrongly identify POND and SLIDE. We are left with the conclusion that AMOEBA is identical to neither. But this seems wrong too; surely fission does not result in death. So just what does happen to AMOEBA? How to respond to this and related cases has been much discussed.1 There are many proposals, each with distinctive strengths and weaknesses. To these Gallois adds his own, which runs as follows. After division, there are two amoebas, POND and SLIDE, each of which existed before division. But it does not follow that there were two amoebas before division. Though POND and SLIDE are numerically distinct after division, they were numerically identical before division. The identity relation can hold temporarily, or occasionally, as Gallois puts it. My sense is that this sort of claim is regarded by most metaphysicians as downright wacky. And yet there is something very natural about it. Why distinguish POND and SLIDE today because they will differ tomorrow? I suspect the “wackiness” reaction has two sources, one based on Leibniz’s Law..

In order to perfectly describe the world, it is not enough to speak truly. One must also use the right concepts - including the right logical concepts. One must use concepts that "carve at the joints", that give the world's "structure". There is an objectively correct way to "write the book of the world". Much of metaphysics, as traditionally conceived, is about the fundamental nature of reality; in the present terms, this is about the world's structure. Metametaphysics - inquiry into the status of metaphysical questions - turns on structure. The question of whether ontological, causal, or modal questions are "substantive" is in large part a question of whether the world has ontological, causal, and modal structure - whether quantifiers, causal relations, and modal operators carve at the joints.

In , Peter van Inwagen asked a good question. (Asking the right question is often the hardest part.) He asked: what do you have to do to some objects to get them to compose something---to bring into existence some further thing made up of those objects? Glue them together or what?1 Some said that you don’t have to do anything.2 No matter what you do to the objects, they’ll always compose something further, no matter how they are arranged. Thus we learned of the fusion of the coins in our pockets and the Eiffel tower.

Some say that presentism precludes time travel into the past since it implies that the past does not exist, but this is a bad argument. Presentism says that only currently existing entities exist, and that the only properties and relations those entities instantiate are those that they currently instantiate. This does in a sense imply that the past does not exist. But if that precluded time travel into the past, it would also preclude the one-second-per-second “time travel” into the future that is ordinary persistence, for presentism accords the future the same ontological status as the past. Instead of quantifying over past and future objects and events, presentists speak a tensed language, regimented with primitive sentential tense operators. For a presentist, a persisting person is one who did exist, and who will exist. Regimented, these claims become: it was the case that she exists, and it will be the case that she exists. The presentist may then apply the same strategy to time travel proper. Suppose Katy travels back to the time of the dinosaurs. The presentist can say that it was the case two hundred million years ago that Katy exists. This claim, which consists of a present-tense statement “Katy exists” embedded within the past tense operator it was the case two hundred million years ago that, is exactly the sort of statement about time that a presentist is free to accept. This has all been made clear by Simon Keller and Michael Nelson ( ). In addition to rebutting the bad argument against the consistency of presentism and time travel, Keller and Nelson argue positively in favor of consistency by showing how to translate David Lewis’s ( ) account of time travel into the presentist’s tensed language. The appearance of con ict between presentism and time travel, they argue, is due only to the fact that most defenders of time travel (for example Lewis) have tended to phrase their defenses in nonpresentist terms. As much as I applaud their rebuttal of the bad argument, I wish to sound a note of caution..

Exotic ontologies are all the rage. Distant from common sense and often science as well, views like mereological essentialism, nihilism, and fourdimensionalism appeal to our desire to avoid arbitrariness, anthropocentrism, and metaphysical conundrums.1 Such views are defensible only if they are materially adequate, only if they can “reconstruct” the world of common sense and science. (No disrespect to the heroic metaphysicians of antiquity, but this world is not just an illusion.) In the world of common sense and science, bicycles survive changes in their parts, billiard balls strike one another, and nothing travels faster than light. The mereological essentialist denies the rst, but offers this replacement: “there exist successions of numerically distinct, but appropriately related, bicycles with different parts” (Chisholm, , chapter ). The nihilist denies the second, but offers this replacement: “there exist X s and Y s such that the X s are arranged billiard-ball-wise, the Y s are also arranged billiard-ball-wise, and the X s strike the Y s”.2 The four-dimensionalist denies the third, but offers this replacement: “no sequences of matter-stages that are related by genidentity travel faster than light”.3 There is room for disagreement over what exactly “reconstruction” amounts to, but at a minimum: when a metaphysical theory reconstructs ordinary sentences φ1. . . as replacement sentences ψ1. . . , ordinary and scienti c evidence must not refute the view that, strictly speaking, it is ψ1. . . rather than φ1. . . that are true. The metaphysician needs reconstruction in order to face the tribunal of experience. An intriguing newcomer to the contemporary scene is the ancient doctrine of monism, the claim that “reality is one”.4 I will argue that, contrary to..

Some philosophers believe that everyday objects are 4-dimensional spacetime worms, that a person (for example) persists through time by having temporal parts, or stages, at each moment of her existence. None of these stages is identical to the person herself; rather, she is the aggregate of all her temporal parts.1 Others accept “three dimensionalism”, rejecting stages in favor of the notion that persons “endure”, or are “wholly present” throughout their lives.2 I aim to defend an apparently radical third view: not only do I accept person stages; I claim that we are stages.3 Likewise for other objects of our everyday ontology: statues are statue-stages, coins are coin-stages, etc. At one level, I accept the ontology of the worm view. I believe in spacetime worms, since I believe in temporal parts and aggregates of things I believe in. I..

Many otherwise reasonable philosophers are impatient with ontology. These philosophers will probably have little time for Objects and Persons, which claims that while there do exist “atoms arranged statuewise”, there do not exist statues; while there do exist atoms arranged tablewise and atoms arranged chairwise, there exist no tables and chairs. Though I join these philosophers, at the end of the day, in rejecting Merricks’s claims, that day is long, whereas they want a quick verdict. But why? Do our impatient friends think that Merricks’s claims are contradictory, analytically false, or otherwise conceptually incoherent? They may say that the conventional meaning of “there exists a statue” is “there exist atoms arranged statuewise”, but this does not stand up to scrutiny. Someone could, of course, just decide to mean such a thing by “there exists a statue”, but then her pronouncements would be irrelevant to Merricks, who intends to be using a..

Presentism is the doctrine that only the present is real. Since ordinary talk and thought are full of quantification over non-present objects, presentists are in a familiar predicament: in their unreflective moments they apparently commit themselves to far more than their ontological scruples allow. A familiar response is to begin a project of paraphrase. Truths appearing to quantify over problematic entities are shown, on analysis, to not involve quantification over those entities after all. But I think that we might be better off abandoning paraphrase altogether. I suggest a project of discovering “underlying truths” rather than paraphrases. I will explore this strategy as applied to defending presentism, but my hope is that lovers of desert landscapes everywhere will herein find words of comfort

In no possible world does a time traveler succeed in killing herearlier self before she ever enters a time machine. So if many,many time travelers went back in time trying to kill theirunprotected former selves, the time travelers would fail inmany strange, coincidental ways, slipping on bananapeels, killing the wrong victim, and so on. Such cases producedoubts about time travel. How could ``coincidences'' beguaranteed to happen? And wouldn't the certainty of coincidentalfailure imply that time travelers are not free to killtheir earlier selves? But if so, what would inhibit theirfreedom? Despite initial appearances, these and other doubtsmay be answered: the possibility of time travel survives yetanother challenge.

This dissertation explores the concepts of naturalness, intrinsicality, and duplication. An intrinsic property is had by an object purely in virtue of the way that object is considered in itself. Duplicate objects are exactly similar, considered as they are in themselves. The perfectly natural properties are the most fundamental properties of the world, upon which the nature of the world depends. In this dissertation I develop a theory of intrinsicality, naturalness, and duplication and explore their philosophical applications. Chapter 1 introduces the notions, gives a preliminary survey of some proposed conceptual connections between the notions, and sketches some of their proposed applications. Chapter 2 gives my background assumptions and introduces notational conventions. In chapter 3 I present a theory of naturalness. Although I take ‘natural’ as a primitive, I clarify this notion by distinguishing and explicating various conceptions of naturalness. In chapter 4 I give a theory of various notions related to naturalness, especially intrinsicality and duplication. I show that ‘intrinsic’ and ‘duplicate’ are interde nable, and then give analyses of these and other notions in terms of naturalness. If, as I think likely, naturalness cannot be analyzed, then what is the proper response? David Lewis suggests: accept naturalness as a primitive. I am sympathetic to this proposal, but not to the form Lewis gives it: chapter 5 contains an argument against Lewis’s theory of naturalness. In chapter 6 I reject the idea that naturalness is analyzable in terms of immanent universals. I focus on the work of D. M. Armstrong. I also criticize Armstrong’s arguments against transcendent universals.

In the process of arguing against all theories of extended material objects made up of simples, Dean Zimmerman has recently argued against the compossibility of continuous closed and continuous open material objects. But it is surely undeniable that point-like material objects are possible; plausible principles of recombination and the principle of unrestricted composition then lead to the possibility Zimmerman rejects. Fortunately, Zimmerman’s arguments can be resisted: what appear to be implausible modal consequences of the compossibility of open and closed continuous material objects turn out to be merely the results of a decision to use ‘material object’ in a certain way