Combining quantum mechanics with special relativity requires (i) that a spacetime representation of quantum states be found; (ii) that such states, represented as extended along equal-time hyperplanes, be invariant when transformed from one frame to another; and (iii) that collapses of states be instantaneous in every frame. These requirements are met using branching spacetime, in which probabilities of outcomes are represented by the numerical proportions of branches on which the outcomes occur. Quantum states of systems are then identified with the probability values, built into spacetime along spacelike hypersurfaces, of all possible outcomes of all possible tests to which the systems can be subjected.

The nature of persistence of physical objects over time has been intensely debated in contemporary metaphysics. The two opposite views are widely known as “endurantism” (or “three-dimensionalism”) and “perdurantism” (“four-dimensionalism”). According to the former, objects are extended in three spatial dimensions and persist through time by being wholly present at any moment at which they exist. On the rival account, objects are extended both in space and time and persist by having “temporal parts,” no part being present at more than one time. Relativistic considerations seem highly relevant to this debate. But they have played little role in it so far. This paper seeks to remedy that situation. I argue that considerations based on the special theory of relativity and the notion of coexistence favor perdurantism over endurantism.

Mark Hinchliff concludes a recent paper, “The Puzzle of Change,” with a section entitled “Is the Presentist Refuted by the Special Theory of Relativity?” His answer is “no.”

I respond by arguing that presentists face great difficulties in merely stating their position in Minkowski spacetime. I round up some likely candidates for the job and exhibit their deficiencies.

Presentism is the view, roughly speaking, that only presently existing things exist. Though presentism offers many attractive solutions to problems in metaphysics, philosophy of language, and philosophy of mind, it faces threats from two main sources: McTaggart and the special theory of relativity. This paper explores the prospects for fitting presentism together with the special theory. Two models are proposed, one which fits presentism into a relativistic setting (the cone model) and one which fits the special theory into a presentistic setting (the surface model). It is concluded that there is no good reason arising from the special theory of relativity for rejecting presentism. Presentism is tenable here and preferable elsewhere.

Throughout this century many philosophers and physicists have gone for the ‘big kill’ regarding tenses. They have tried to show via McTaggart's paradox and special relativity that tenses are logically and physically impossible, respectively. Neither attempt succeeds, though as I argue, both leave their mark. In the first two sections of the paper I introduce some conceptual difficulties for the tensed theory of time. The next section then discusses the standing of tenses in light of special relativity, especially recent work by Stein on the topic. I argue that, Stein's possibility theorem notwithstanding, special relativity is inconsistent with any philosophically interesting conception of tense. Finally, I search for help for tenses in the broader context of quantum theory, Lorentzian interpretations of time dilation/length contraction, and general relativistic spacetimes. I suggest that these avenues do not provide tenses the home for which some have hoped.

Is tense real and objective? Can the fact that something is past, say, be wholly objective, consistent with modern physics? I believe that it can. But some hold that for tense to be real, then a certain ontological doctrine must also hold. There must be a fact of the matter as to what really, truly, exists at each time. For example, it is held that only what is now really exists. This is the doctrine of presentism. Alternatively, that only what is now or past really exists; following Savitt, I shall call this possibilism. But on either view there is a problem with special relativity.

Most contemporary chemists consider quantum mechanics to be the foundational theory of their discipline, although few of the calculations that a strict reduction would seem to require have ever been produced. In this essay I discuss contemporary algebraic and diagrammatic representations of molecular systems derived from quantum mechanical models, specifically configuration interaction wavefunctions for ab initio calculations and molecular orbital energy diagrams. My aim is to suggest that recent dissatisfaction with reductive accounts of chemical theory may stem from both the inability of standard accounts of reduction to incorporate the diverse forms of representation found in chemical practice and our philosophical predilection to analyze all connections between theories in terms of logical reduction.

Real kinds or categories, according to conventional wisdom, enter into lawlike generalizations, while nominal kinds do not. Thus, gold but not jewelry is a real kind. However, by such a criterion, few if any kinds or systems of classification employed in the social science are real, for the social sciences offer, at best, only restricted generalizations. Thus, according to conventional wisdom, race and class are on a par with telephone area codes and postal zones; all are nominal rather than real. I propose an account of real kinds that recognizes the current reality of race but not zip codes and shows how a kind can be both constructed and real. One virtue of such an understanding of realism is the light shed on our current practice of racial classification. Race is not a real biological kind but neither is race a myth or illusion. However, the question of whether a social kind is real is separate from whether the category is legitimate. W. E. B. Du Bois maintained that while there are no biological races, race is real and should be conserved. My aim, in this paper, is not to argue for the legitimacy or conservation of race but to defend Du Bois's idea that kinds of people can be both made up and real and provide an understanding of realism that does justice to the social sciences.

We often legitimately ascribe reality both to social and to natural kinds. But the bases for these ascriptions are not entirely the same. In both cases, reality is typically determined by what characterizations of causal factors are indispensable to adequate explanation. Nonetheless, a psychological role as part of an identity that instances embrace is sometimes, distinctively, a condition for ascribing reality to a social kind. Although such assessments of reality can be construed as employing a standard of causal activity shared with natural science, they reveal a distinctive moral dimension in the bases for ascribing reality to social kinds.

Race was once thought to be a real biological kind. Today the dominant view is that objective biological races don't exist. I challenge the trend to reject the biological reality of race by arguing that cladism (a school of classification that individuates taxa by appeal to common ancestry) provides a new way to define race biologically. I also reconcile the proposed biological conception with constructivist theories about race. Most constructivists assume that biological realism and social constructivism are incompatible views about race; I argue that the two conceptions can be compatible.

This paper argues that realism issue in the social sciences is not one that can be decided by general philosophical arguments that evaluate entire domains at once. The realism issue is instead many different empirical issues. To defend these claims, I sort issues that are often run together, explicate and criticize several standard realist and antirealist arguments about the social sciences, and use the example of the productive/nonproductive distinction to illustrate the approach to realism questions that I favor.