This paper argues that the most famous objection to backward time travel can carry no weight. In its classic form, the objection is that backward time travel entails the occurrence of impossible things, such as auto-infanticide—and hence is itself impossible. David Lewis has rebutted the classic version of the objection: auto-infanticide is prevented by coincidences, such as time travellers slipping on banana peels as they attempt to murder their younger selves. I focus on Paul Horwich‘s more recent version of the (...) objection, according to which backward time travel entails not impossible things, but improbable ones—such as the string of slips on banana peels that would be required to stop a determined auto-infanticidal maniac from murdering her younger self—and hence is itself highly improbable. I argue that backward time travel does not entail unusual numbers of coincidences; and that, even if it did, that would not render its occurrence unlikely. (shrink)

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. (shrink)

Precis of my book by this title, for a symposium.

One of the questions that is addressed, from various perspectives, is the origin of time-asymmetry. Given the time-symmetry of the dynamical laws, all inferences about the future that are derivable from a dynamical theory are matched by inferences about the past. For Huw Price, who discusses the origins of cosmological time asymmetry, this is reason to treat all time-asymmetric cosmological theories with caution. He dismisses both the inflationary model and Stephen Hawking’s proposal to account for time-asymmetry with his famous “no (...) boundary condition.” Instead, on the basis of the fact that we have no a priori reasons to distinguish between initial and final conditions, he advocates Gold’s time-symmetric model for the universe, in which the thermodynamical arrow of time is tied to the expansion of the universe, so that in the contracting phase towards the big crunch, entropy decreases. (shrink)

Time is generally thought to be one of the more mysterious ingredients of the universe. In this intriguing book, Paul Horwich makes precise and explicit the interrelationships between time and a large number of philosophically important notions.Ideas of temporal order and priority interact in subtle and convoluted ways with the deepest elements in our network of basic concepts. Confronting this conceptual jigsaw puzzle, Horwich notes that there are glaring differences in how we regard the past and future directions of time. (...) For example, we can influence the future but not the past, and can easily gain knowledge of the past but not of the future. Moreover we see a profusion of decay processes but little spontaneous generation of order; time appears to "flow" in one privileged direction, not the other; and we tend to explain phenomena in terms of antecedent circumstances, rather than subsequent ones. Horwich explains such time asymmetries and examines their bearing on the nature of time itself.Asymmetries in Time covers many notoriously difficult problems in the philosophy of science: causation, knowledge, entropy, explanation, time travel, rational choice, laws of nature, and counterfactual implication -- and gives a unified treatment of these matters. The book covers an unusually broad range of topics in a lucid and nontechnical way and includes alternative points of view in the philosophical literature. (shrink)

Four- Dimensionalism defends the thesis that the material world is composed of temporal as well as spatial parts. This defense includes a novel account of persistence over time, new arguments in favour of the four-dimensional ontology, and responses to the challenges four- dimensionalism faces." "Theodore Sider pays particular attention to the philosophy of time, including a strong series of arguments against presentism, the thesis that only the present is real. Arguments offered in favour of four- dimensionalism include novel arguments based (...) on time travel, the debate between spacetime substantivalists and relationalists, and vagueness. Also included is a comprehensive discussion of the paradoxes of coinciding material objects, and a novel resolution of those paradoxes based on temporal counterpart theory. In conclusion Sider replies to prominent objections to four- dimensionalism, including discussion of the problem of the rotating homogenous disk. (shrink)