Joshua Mozersky

Many argue that the standard understanding of the second law of thermodynamics combined with the supposition, backed by recent scientific evidence, that the future is infinite entails that one is, most likely, a momentary Boltzmann brain that will quickly disintegrate into the cosmos. The argument is as follows: (1) Given infinite time, the universe will eventually reach thermodynamic equilibrium; (2) once there, every possible fluctuation away from equilibrium, no matter how improbable, will recur, ad infinitum; (3) those fluctuations that create stable, long-lived creatures, such as we take ourselves to be, will be extremely rare compared to those that create short-lived brains that mistakenly think they are ordinary human beings; hence, by statistical reasoning, (4) one is, with overwhelming probability, just a fleeting instantiation of experience. I argue that this reasoning is invalid since it rests on an error regarding the relationship between infinite sets and their subsets. Once this error is eliminated, the power of the argument fades, and the evidence that we are ordinary human beings becomes decisive. Surprisingly, I find that the best argument for the Boltzmann brain hypothesis requires the assumption that the future is very long but finite.

McTaggart's argument that time is unreal was agreed by few philosophers, but it opened up a great split among twentieth‐century philosophers of time over the question of whether time must form an A‐series (“A‐theory”) or whether a B‐series suffices for the reality of time (“B‐theory”). This chapter discusses the most prominent twentieth‐century arguments in favor of the negative responses to questions that were seen to be especially important in deciding this matter. It begins with the puzzle of change because if one accepts that temporal predicates indeed any predicates that can report change are in fact relations, then the appeal of the four pillars of the B‐theory becomes apparent. The pillars of B‐theory are (i) any conception of temporal passage as the gain and loss of non‐relational, tensed properties is incoherent; (ii) the underlying, logical structure of tensed language is tenseless; (iii) eternalism; and (iv) temporal experience is explainable B‐theoretically.

Ian Hacking’s wide-ranging and penetrating analysis of science contains two well-developed lines of thought. The first emphasizes the contingent history of our inquiries into nature, focusing on the various ways in which our concepts and styles of reasoning evolve through time, how their current application is constrained by the conditions under which they arose, and how they might have evolved differently. The second is the mistrust of the idea that the world contains mind-independent natural kinds, preferring nominalism to ‘inherent structurism’. These two pillars of thought seem at first to be mutually reinforcing: the lack of natural structure can help make sense of scientific variability and revision, while variability and revision provide reason to suspect that natural structure is little more than idealization. In what follows, I argue that these two pillars not only fail to support each other, but in fact conflict. One of them must fall, and it is clear which.

Tenseless theories of time entail that the only temporal properties exemplified by events are earlier than, simultaneous with, and later than. Such an account seems to conflict with our common experience of time, which suggests that the present moment is ontologically unique and that time flows. Some have argued that only a tensed account of time, one in which past, present and future are objective properties, can do justice to our experience. Any theory that claims that the world is different from how we experience it must nonetheless be consistent with the having of that experience. Accordingly, in this essay I defend the tenseless theory by arguing that it can indeed account for certain key features of our experience of time without recourse to tensed properties.

In this essay I respond to Quentin Smith's chargethat `the date-analysis version ofthe tenseless theory of time cannot give adequateaccounts of the truth conditions ofthe statements made by tensed sentence-tokens'(Smith 1999, 236). His argument isbased on an analysis of certain counterfactualsituations that is at odds with thedate-analysis account of language and hence succeedsonly in begging the questionagainst that theory. To anticipate: his argumentfails if one allows that temporalindexicals such as `now' rigidly designate theirtime of utterance, something thedate-analyst can happily admit whether she adheresto an absolute or relationalmetaphysics of time.

Tenseless theories of time entail that earlierthan, later than and simultaneous with (i.e.,McTaggart's `B-series') are the only temporalproperties exemplified by events. Such theories oftencome under attack for being unable to satisfactorilyaccount for tensed language. In this essay I arguethat tenseless theories of time are capable of twofeats that critics, such as Quentin Smith, argue arebeyond their grasp: (1) They can coherently explainthe impossibility of translating all tensed sentencesby tenseless counterparts; (2) They can account forcertain obviously valid entailment relations betweentensed sentence types. In analyzing tensed entailmentrelations tenselessly, I favor a date analysis oftensed language over a token-reflexive theory. Theupshot is that tenseless theories of time are notundermined by the linguistic facts.

In this essay I address the issue of whether Einstein's Special Theory of Relativity counts against a tensed or "A-series" understanding of time. Though this debate is an old one, it continues to be lively with many prominent authors recently arguing that a genuine A-series is compatible with a relativistic world view. My aim in what follows is to outline why Special Relativity is thought to count against a tensed understanding of time and then to address the philosophical attempts to reconcile the two theories. I conclude that while modern physics on its own does not rule out the possibility of a real A-series, the combination of Einstein's theory and the philosophical arguments against tense is decisive. The upshot is that the tenseless or "B-series" view of time is the best one.

Different beliefs concerning the metaphysical status of tense divide philosophers into two camps. Those who embrace a tensed theory of time argue that past, present and future correspond to genuine ontological distinctions. Those who deny the reality of such distinctions espouse a tenseless theory of time . In this essay I defend a tenseless account. ;I begin with an examination of the most prominent ontological conceptions of tense, finding them to be incoherent at worst, highly implausible at best. I then turn my attention to Einstein's Special Theory of Relativity, arguing that, properly understood, it demonstrates that tenses could not be physically realized. The upshot is that tense is not a philosophically viable notion. If time is real, it must be tenseless. ;Therefore, the choice is between tenseless time and some sort of temporal idealism. Defending the former alternative, I focus my efforts, in the second part of the essay, on responding to the most important objections to a tense-free ontology. I argue that tenseless time: can explain the semantics of tensed sentences; does not entail fatalism or determinism of any kind; and is consistent with our mental experience. These results indicate that tense is a feature of perception, not a property of time itself. ;In the third part of the essay I argue that theories that constrain truth epistemically are poorly motivated and implausible. Therefore, in considering the status of tense, ontological considerations can rightly take precedence over epistemic concerns. This defuses objections to tenseless time that are based on the obvious fact that the past, present and future differ with respect to their epistemic accessibility. It is, therefore, consistent to hold that time is epistemically asymmetric but ontologically symmetric

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