Does time pass? Well of course it does. Iconoclasts and gadflies might deny it, but (as my parents used to say) they’re just looking for negative attention. It is therefore frustrating to be told, as I have been, that one's theory of time is false because it leaves out the passage of time. In a way, Objective Becoming is a defence of the theory I prefer against this accusation. That theory is the block universe theory of time.1 The bumper-sticker version of the block universe theory says that time is a dimension of reality that is a lot like space. Since space does not move, or flow, neither does time. But that’s okay; time does not need to move or flow in order for it to be true to say that time is passing. At least that’s what I think. But some philosophers do think that time needs to move, or at least change in some way, for it to be true that time is passing. Since these philosophers, and I, disagree about what it takes for it to be true that time is passing, it’s better not to frame our debate as a debate about whether time passes. Instead we should focus on the features we can all agree that the block universe theory and its rival theories have. Objective Becoming frames the block universe theory and its rivals in more or less the meta-metaphysical framework Ted Sider advocates (Sider 2011).2 Some (true) descriptions of reality describe reality in a fundamental way, while others describe it in a non-fundamental way. The fundamental descriptions use only fundamental vocabulary; descriptions that do not use only fundamental vocabulary are non-fundamental.3 In this framework, a theory of time must do two things: say what the ‘temporal aspects of reality’ are like, fundamentally speaking, and at least gesture at what the ‘metaphysical truth-conditions’ are for non-fundamental ways of speaking of those temporal aspects. A metaphysical truth-condition has the form: ‘S’ is true in context C iff …, where ‘S’ is replaced by a non-fundamental sentence and the dots are replaced by a sentence that uses only fundamental vocabulary. (The connective ‘iff’ should be read as something stronger than material equivalence, maybe even as something stronger than necessary equivalence – but the exact details of its meaning won’t matter here.) If we work under the assumption that Newtonian mechanics on its standard interpretation is true, then the block universe theory says that, fundamentally speaking, there is such a thing as time, just as there is such a thing as space; that time forms a one-dimensional continuum, just as space forms a three-dimensional one; the story goes on, but this summary must be brief. The theory also says that tensed verb forms are non-fundamental, and offers truth-conditions for sentences containing them. For example, ‘Jones used to be 4 feet tall’, as used in a context where the time of speech is t, has the truth-condition that Jones is 4 feet tall at a time earlier than t. Here ‘is’ is a tenseless form of be that does not occur in English. (This is only an approximation to the metaphysical truth-condition, since ‘feet’ and ‘tall’ and ‘earlier’ are also non-fundamental; since what is relevant in debates in the metaphysics of time is whether tense is fundamental, I pretend that a modification of English that lacks tensed verb forms is a fundamental language.) I haven’t done any surveys, but I’d guess that the most popular alternative to the block universe theory of time is presentism. The most natural version of presentism says, against the block universe theory, that tense is fundamental, and also says, again against the block universe theory, that fundamentally speaking time does not exist (after all, it is not needed to give truth-conditions to tensed sentences anymore). But I don’t think that presentism is the best alternative to the block universe theory. The best alternative, I think, is the moving spotlight theory. It’s better not just than presentism, but also the ‘growing block’ theory of time and the ‘branching future’ theory of time. A large proportion of Objective Becoming, the first 10 chapters in fact, is spent sizing up, and also propping up, the moving spotlight theory. So what does the moving spotlight theory say? As a first pass it says that exactly one time is present and that which time that is changes: later times will be present, earlier times were present. Of course, the block universe theory says that these sentences are true too, but in that theory their truth is due to the context-sensitivity of ‘present’ (and of tense). What makes the moving spotlight theory different is that their truth is not due to these factors; in fact, the theory says that ‘present’ is a fundamental piece of vocabulary. What about tense? Does the moving spotlight theory also says that tensed verbs are among the fundamental pieces of vocabulary? At this point it become misleading to speak of ‘the’ moving spotlight theory; a variety of versions of the theory diverge here. Objective Becoming focuses on two. The first, the ‘supertense’ version of the moving spotlight theory (which I abbreviate ‘MST-Supertense’; I am not proud of the name), says that among the fundamental pieces of vocabulary are tensed verb forms. Those tensed verb forms, however, differ in meaning from analogous forms in English, so to avoid confusion I spell them differently. The past form of be in the fundamental language, for example, is spelled ‘super-was’; in general, the verbs in the language inflect for ‘supertense’. This version of the moving spotlight theory says that, fundamentally speaking, exactly one time super-is present, times later than the present time super-will be present, and so on. In this theory, English sentences containing tensed verb forms have truth-conditions which may be stated using supertensed verbs and quantifiers ranging over times. For example, the theory says that ‘Jones used to be 4 feet tall’ super-is true (in English) iff it super-was the case that Jones super-is tall at the present time.4 Another version of the theory, which I call MST-Time, breaks from the block universe theory not by saying that tense is fundamental, but by asserting a relativity of facts to instants of time that goes beyond anything in the block universe theory. According to this theory, from the perspective of each time, that time is present; it is the fact that later times are present from the perspectives of later times that, in the theory, underwrites the truth of the claim that ‘presentness’ ‘moves’ along the series of times. (A third version of the theory, ‘MST-Supetime’, also appears in the book; it says that later times are present at later supertimes. But its appearance is just a ladder that is kicked away.) The moving spotlight theory has come in for a lot of bad press, so in the middle of the book I cross the aisle to defend it against some bad arguments. The theory is not inconsistent, as McTaggart has been thought to have shown; and the theory does not have an incoherent answer to the question of how fast time passes, as many of my fellow pro-blockers have alleged. If those arguments aren’t good grounds for preferring the block universe theory, what are? I don’t think we can decide what theory of time to believe by simply looking at them all, consulting some a priori intuitions about what the passage of time consists in, and saying, ‘Aha! That one is the one that gets the passage of time right, so it is the true theory.’ Deciding between the theories is going to require more evidence and argument than that. I discuss two kinds of evidence, the first kind esoteric and the second kind available to anyone who sits on a couch for 5 minutes. The esoteric evidence ultimately comes from complicated physics experiments − the experiments that physicists took to establish Einstein’s special, and then general, theories of relativity. There is a tradition of arguing that theories of time like the moving spotlight theory are inconsistent with the theory of relativity, and so must be false. I show, against this, that the moving spotlight theory can be made consistent with the theory of relativity in many different ways. (Consistency, of course, is a low bar; the block universe theory might still be more strongly supported by the evidence for relativity theory than is the moving spotlight theory. Although I believe this to be the case, I do not push the point in the book.) The easily available evidence is evidence that comes ‘from experience’. It’s a common thought that in some sense the world would not look (or sound) like this if the block universe theory were true, but would if a theory like the moving spotlight theory were true. The problem with this argument is unclarity in what ‘like this’ means, and I discuss three ways to make it clear, and three arguments that come out of them. Maybe the claim is that the way our experience represents the world (e.g. the way our visual experience represents the scene before our eyes) favours the moving spotlight theory; or maybe the claim is that the fact that our experience has a certain ‘phenomenal character’ favours the moving spotlight theory. Both these claims, I argue, are false. I also discuss a third way of construing the argument from experience. According to the block universe theory, I may be at one time looking at a green paint chip, and at another time looking at a red paint chip. In that theory, then, I bear the same relation to the experience as of the green chip as I do to the experience as of the red chip. But surely I don’t! The experience as of the red chip is the one I am having, and this fact has been left out of the theory. The moving spotlight theory, the argument continues, does not leave this out: it says that the experience I am having is the one that occurs at the present time. This argument is all smoke and mirrors, though; in short, the block universe theory does say that the red chip is the one I am having, since ‘the one I am having’ refers to the experience I am having at the time of speech, which in this case is the time when I am looking at the red chip. Footnotes 1 It is sometimes also called, in one of the worst choices of philosophical terminology ever, the ‘B-theory’ of time. 2 I didn’t choose this framework out of any feeling of necessity. I haven’t actually thought through whether that framework is essential to my defence. 3 Sider formulates his meta-metaphysics so as not to require the use of ‘fundamental’ as a predicate of words and phrases, but for simplicity I will use it that way. 4 Here ‘the present time’ is non-rigid. There are actually two versions of MST-Supertense, which disagree on the truth-conditions for ‘ordinary’ tensed sentences; this is what the version with ‘strong’ truth-conditions says. Reference Sider T. 2011. Writing the Book of the World . Oxford: Oxford University Press. Google Scholar CrossRef Search ADS © The Authors 2018. Published by Oxford University Press on behalf of The Analysis Trust. All rights reserved. For Permissions, please email: email@example.com
Analysis – Oxford University Press
Published: Jan 1, 2018
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