Theodore Sider

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

An intrinsic property, as David Lewis puts it, is a property "which things have in virtue of the way they themselves are", as opposed to an extrinsic property, which things have "in virtue of their relations or lack of relations to other things".1 Having long hair is an intrinsic property; having a long-haired brother is not. Intuitive as this notion is (and valuable in doing philosophy, I might add), it seems to resist analysis. Analysis, that is, to “quasi-logical” notions such as necessity, spatiotemporal location: using stronger tools, Lewis has given an analysis of intrinsicality that I take to be roughly correct. Lewis initially described intrinsic properties in his 1983 paper "Extrinsic Properties" as follows

Logic begins but does not end with the study of truth and falsity. Within truth there are the modes of truth, ways of being true: necessary truth and contingent truth. When a proposition is true, we may ask whether it could have been false. If so, then it is contingently true. If not, then it is necessarily true; it must be true; it could not have been false. Falsity has modes as well: a false proposition that could not have been true is impossible or necessarily false; one that could have been true is merely contingently false. The proposition that some humans are over seven feet tall is contingently true; the proposition that all humans over seven feet tall are over six feet tall is necessarily true; the proposition that some humans are over seven feet tall and under six feet tall is impossible, and the proposition that some humans are over nine feet tall is contingently false. Of these four modes of truth, let us focus on necessity, plus a fifth: possibility. A proposition is possible if it is or could have been true; hence propositions that are either necessarily true, contingently true, or contingently false are possible. Notions that are similar to the modes of truth in being concerned with what might have been are called modal. Dispositions are modal notions, for example the disposition of fragility. Relatedly, there are counterfactual conditionals, for example “if this glass were dropped, it would break.” And the notion of supervenience is modal.1 But let us focus here on necessity and possibility. Modal words are notoriously ambiguous (or at least context-sensitive2). I may reply to an invitation to give a talk in England by saying “I can’t come; I have to give a talk in California the day before”. This use of “can’t” is perfectly appropriate. But it would be equally appropriate for me to say that I could cancel my talk in California (although that would be rude) and give the talk in England instead. What I cannot do is give both talks..

Possible worlds present a formidable challenge for the lover of desert landscapes. One cannot ignore their usefulness; they provide, as David Lewis puts it, “a philosophers’ paradise”.1 But to enter paradise possibilia must be fit into a believable ontology. Some follow Lewis and accept worlds at face value, but most prefer some other choice from the current menu. Part of Chihara’s book is a critical discussion of some of these menu options: Lewis’s modal realism, Alvin Plantinga’s abstract modal realism, Graeme Forbes’s anti-realism and Gideon Rosen’s modal fictionalism. These discussions are very detailed and conversant with the literature. The discussions of Forbes and of paradox within Plantinga’s system are particularly enlightening. The rest of the book is devoted to Chihara’s positive project: developing an account of the status of model theory for non-modal logic, and then applying it to the modal case. The prize is an understanding of possible worlds semantics that requires no commitment to possible worlds at all What does the relativized notion of truth in an interpretation studied in model theory have to do with plain old truth? Chihara’s answer involves “connecting theorems” that relate truth-in to truth. A “natural-language proto-interpretation of the sentential calculus” is a function that assigns meanings of declarative sentences of English to sentence letters. Where I is an NLPI of SC and φ is a sentence letter, Chihara uses ‘[φ/I ]’ to refer to “φ with the meaning it has been assigned by I ” ; where φ is not atomic, he says

Statues and lumps of clay are said by some to coincide - to be numerically distinct despite being made up of the same parts. They are said to be numerically distinct because they differ modally. Coincident objects would be non-modally indiscernible, and thus appear to violate the supervenience of modal properties on nonmodal properties. But coincidence and supervenience are in fact consistent if the most fundamental modal features are not properties, but are rather relations that are symmetric as between coincident entities, relations such as "opposite-possibly surviving being squashed"