Theodore Sider

In my book Four-dimensionalism (chapter 4, section 9), I argued that fourdimensionalism – the doctrine of temporal parts – follows from several other premises, chief among which is the premise that existence is never vague. Kathrin Koslicki (preceding article) claims that the argument fails since its crucial premise is unsupported, and is dialectically inappropriate to assume in the context of arguing for four-dimensionalism. Since the relationship between four-dimensionalism and the non-vagueness of existence is not perfectly transparent, I think the argument would retain some interest even if the premise were wholly unsupported; it would show that anyone who accepts that premise (which seems reasonable enough to me though perhaps not to others) must accept four-dimensionalism. Still, Koslicki is right that my defense of the premise was thin. So I will now try to do better. The new defense will have further premises, which could ultimately be rejected by opponents of four-dimensionalism, and so the argument retains the form: anyone who thinks certain things (which seem reasonable enough to me though perhaps not to others) must believe four-dimensionalism. But that’s metaphysics for you. I should also say that, in addition to the material on vague existence, there is more in Koslicki’s excellent paper which I cannot discuss here. I agree with much of it;1 and where we disagree there are formidable challenges, some of which I hope to address in the future

According to four dimensionalism, the material world is divided into momentary stages. In a four-dimensional world, which objects are the ordinary things, the things we normally name and quantify over? Aggregates of stages, according to most four-dimensionalists, but according to stage theorists (or exdurantists), ordinary objects are instead to be identified with the stages themselves. (A temporal counterpart theoretic account of de re temporal predication is then given.) This paper argues that a stage theorist is best positioned to accept David Lewis's argument from temporary intrinsics for four-dimensionalism, since stage theorists are the only four-dimensionalists who attribute monadic temporary intrinsic properties to ordinary things.

We often speak of an object being composed of various other objects. We say that the deck is composed of the cards, that a road is the sum total of its sections, that a house is composed of its walls, ceilings, floors, doors, etc. Suppose we have some material objects. Here is a philosophical question: what conditions must obtain for those objects to compose something? In his recent book Material Beings, Peter van Inwagen addresses this question, which he calls the ‘special composition question’; his answer is:1 (1) For any material objects X , the X s compose something iff the activity of the X s constitutes a life, or there is only one of the Xs. Additionally, he accepts a simpler thesis that follows from (1):2 (2) Every material object is either a mereological atom or a living thing, where a mereological atom is an object lacking proper parts. (2) may seem radical. If it is true then there are no tables, chairs, planets, protons, galaxies, gas stations, etc. But van Inwagen does not hold it lightly— there are serious difficulties with alternate views. Moreover, he claims that..

For most us, learning which quantum theory correctly describes human bodies will not affect our attitudes towards our loved ones. On the other hand, a child’s discovery of the nature of meat (or an adult’s discovery of the nature of soylent green) can have a great effect. In still other cases, it is hard to say how one would, or should, react to new information about the underlying nature of what we value—think of how mixed our reactions are to evidence of cultural determinism or atheism, or of how mixed our reactions would be to learning that we all live in the Matrix. (Indeed, maybe there is no objective fact about how we should react. Derek Parfit’s (1984, section 95) fear of death diminished when he became convinced of certain theses about the metaphysics of personal identity. Perhaps there is no objective fact of the matter as to whether this was rational; perhaps it was rational for him but would not be for others.) What can metaphysics contribute to the question of the evil of death? It cannot, on its own, settle the question, since there is no simple rule telling us how to adjust value in light of new information about underlying nature. Given a clear view of the nature of death, there will remain the question of its disvalue. However, metaphysics can help us attain this clear view. Moreover, a clear conception of what metaphysical positions do and don’t say, and a clear conception of how metaphysics works in general, can remove impediments to a rational appraisal of the evil of death.

Logic for Philosophy is an introduction to logic for students of contemporary philosophy. It is suitable both for advanced undergraduates and for beginning graduate students in philosophy. It covers (i) basic approaches to logic, including proof theory and especially model theory, (ii) extensions of standard logic that are important in philosophy, and (iii) some elementary philosophy of logic. It emphasizes breadth rather than depth. For example, it discusses modal logic and counterfactuals, but does not prove the central metalogical results for predicate logic (completeness, undecidability, etc.) Its goal is to introduce students to the logic they need to know in order to read contemporary philosophical work. It is very user-friendly for students without an extensive background in mathematics. In short, this book gives you the understanding of logic that you need to do philosophy.

I am now typing on a computer I bought two years ago. The computer I bought is identical to the computer on which I type. My computer persists over time. Let us divide our subject matter in two. There is first the question of criteria of identity, the conditions governing when an object of a certain kind, a computer for instance, persists until some later time. There are secondly very general questions about the nature of persistence itself. Here I include the question of temporal parts, as well as certain familiar paradoxes (e.g., the statue and the lump). Following John Perry (1975, Introduction), let us characterize a criterion of identity over time for F s as a way of filling in φ in the following schema: Stages S1 and S2 belong to some continuing F iff φ Defenders of temporal parts (see below) regard S1 and S2 as being temporal parts of the continuing F ; others regard S1 and S2 as different stages in the life history of the continuing F . Thus each camp can make use of Perry’s formula. It is traditional to divide such criteria into those governing persons and those governing anything else. It is further traditional to say that the criterion of identity over time for non-persons involves spatiotemporal continuity. An excellent discussion is Eli Hirsch’s The Concept of Identity1, which utilizes the notion of continuity under a sortal. Kind-terms, or sortals, are terms that specify what kind of or sort of thing an object is. Examples include ‘tree’, ‘car’, and ‘mountain’. Where F is a sortal, Hirsch’s analysis is roughly that stages belong to the same F iff they are connected by a spatiotemporally and qualitatively continuous sequence of F -stages. Unmodified, this analysis prohibits temporally discontinuous entities, such as a watch that is taken apart and then reassembled. Hirsch discusses the necessary modifications. Spatiotemporal continuity analyses face a problem when applied to the persistence of matter. The literature here has been dominated by discussion of examples provided by David Armstrong (1980) and Saul Kripke (unpublished....

"Composition as identity" is the radical claim that the whole is identical to the parts - radical because it implies that a single object can be identical to many objects. Composition as identity, together with auxiliary assumptions, implies the principle of "collapse": an object is one of some things if and only it is part of the fusion of those things. Collapse has important implications: the comprehension principle of plural logic must be restricted, plural definite descriptions such as "the Cheerios in the bowl" are empty, Composition as identity does not preclude emergent properties (contrary to what McDaniel has argued), and drastic simplifications of mereological and logical ideology are extensionally available.

In an article in Scientific American (March 1994, pp. 68–74) entitled “The Quantum Physics of Time Travel”, Oxford physicist David Deutsch and Oxford philosopher Michael Lockwood give a defense of the physical possibility of time travel based on the “Many Worlds” interpretation of quantum mechanics. This positive view of theirs is not my concern, however—I want to quarrel with their argument that time travel cannot be accommodated in any other way.1 The best way to spell out the traditional “grandfather paradox” that appears to threaten the possibility of time travel involves the notion of ability, or personal possibility, or free will. An example of David Lewis’s: Tim travels back in time with the intent to kill his grandfather.2 Let us fix the case as one in which Tim in fact will not kill Grandfather; still, it seems that he can kill Grandfather because he is a good shot, has a gun, and is alone with Grandfather at close range. As Lewis says, Tim “has what it takes” to kill Grandfather. However, it is also compelling that Tim cannot kill Grandfather, because if Grandfather had been killed in his youth, Tim would not have existed to kill him. It is important to realize that the paradox essentially involves the notion of ability. No inconsistency results from supposing that Tim does not kill Grandfather. As for the case in which Tim does kill Grandfather, there are various possibilities. We could tell a consistent time travel story in which Tim kills Grandfather, but Grandfather is miraculously resurrected. Or one in which Tim kills Grandfather, but in which Grandfather has already had a child. Or one in which Tim kills Grandfather permanently, before Grandfather has any children, but in which Tim’s grandfather is someone other than Grandfather. As for the story in which Tim both kills Grandfather permanently in such a way that Grandfather has no children, and also is descended from Grandfather, this is an inconsistent time travel story; but of course the existence of some....