Can Anything Be Extended in Time?

Our question, then, is this: can we properly talk about time as being a dimension of reality in which concrete things are extended? I think that our answer to this should depend on whether we believe that the tensed or the tenseless view of time is correct. If the tensed view is correct, then I think we cannot properly regard time as being such a dimension of reality, and accordingly cannot accept a perdurance account of the persistence of objects, given my understanding of what such an account implies (namely, the existence of temporally extended entities). Now, it is not my current task to demonstrate beyond all question that the tensed view of time is correct. The most I hope to do is to show why the tensed view cannot, while the tenseless view must, regard persisting objects as being temporally extended.

Since space provides the paradigm of extension, we can conceive of time as a dimension in which things can be extended only in so far as we can find suitable similarities between space and time. The only case that can be made for there being a relevant similarity, it appears to me, rests upon a comparison between the relations between different points on a line and the relations between different times. Now, the tenseless theory of time, with its exclusive reliance on B-series terminology, does indeed make space and time appear relevantly similar. For, on this view, the earlier/later

relations between times (and events) suffice to define a ‘betweenness’ relation on them which is entirely analogous to the betweenness relation of points on a line. (A time t is between two other times t? and t= just in case t is later than t?

and earlier than t= or t is earlier than t? and later than t=—and similarly with events; moreover, all times are thus related to one another, in a unique linear sequence.) Quite crucial here is the fact that the tenseless theory makes no ontological distinction between different times, nor between the existence of things at different times—for this precisely parallels the spatial case. Of course, there is still the anisotropy of time—its directedness—to consider, but this doesn't appear to be a particularly important difference between time and space as far as the tenseless theory is concerned, or, at least, not important enough to undermine the theory's commitment to an extensional view of time.

There seems, then, to be no good reason why a tenseless theorist of time should regard space, but not time, as being a dimension of reality in which things are extended. But matters are, I believe, quite otherwise for the tensed theorist of time. For him the fundamental notions are of past, present, and future, which have no spatial analogues. It is true, no doubt, that the tenseless theorist will urge that there is a close parallel between ‘now’ and ‘here’: but the tensed theorist should vigorously deny this, because while he may happily allow that the truth-conditions of sentences containing spatial indexicals such as ‘here’ can be stated in a metalanguage which does not itself deploy spatial indexicals, he will—as we have seen—be well advised to hold in contrast that tensed sentences can only be provided with tensed truth-conditions. In short, the tensed theorist may agree with the tenseless theorist about the semantics of ‘here’, but should not do so about the semantics of ‘now’.

On the tenseless view, any event e is tenselessly between at least two other events e? and e=—with the possible exceptions of a first and a last event at the ends of time—just as, on this view, any point is tenselessly between at least two others on a line. But on the tensed view, although e can be said, for example, to have occurred less long ago than e? and longer ago than e=, this doesn't license us to say that e has or had some ‘betweenness’ relation to e? and e= in anything like the sense which obtains in the spatial case. For, on the tensed view, e? had already ceased to exist when e came into existence, and the latter had ceased to exist when e= came into existence. Accordingly, we do not have here a relationship between entities which are in any sense coexistent, and for that reason not one at all like that between points on a line. Now, it is true that a tenseless theorist will also say that, in one sense, e, e?, and e= do not coexist—namely, in the sense that they do not all exist at the same time. Yet, for the tenseless theorist these events do still coexist in another sense, in as much as i t i s

tenselessly true of all of them that they exist, simpliciter—for, on the tenseless view, ‘e exists at t’ clearly entails ‘e exists’, simpliciter. (If you like, for the tenseless theorist all these events coexist, tenselessly, in the same possible world—the actual world—and differ not at all from one another in respect of their ontological status within that world, but only in respect of their temporal location within in.) Clearly, it would indeed be simply mistaken to describe the tenseless theorist as treating all events as being cotemporal. But the ‘co’ in ‘coexistent’ need not be taken to mean ‘at the same time’—it may be taken to mean ‘together’ in some other sense, if one is available. And then the point is that for the tenseless theorist another such sense is undoubtedly forthcoming, whereas for the tensed theorist there is simply no sense in which e, e?, and e= can be said to coexist, because on this view existence can only be ascribed to them in a tensed way—and in that way they cannot be said to coexist.

My claim, then, is that any ‘betweenness’ relation relevantly akin to that relating points on a line is a relation between items which must in some sense coexist—but that the tensed theorist allows no such sense for events separated in time.

And this is why I conclude that the tenseless theory alone treats time as a dimension of reality in which things are extended, and accordingly treats persisting objects as having temporal parts (in the only metaphysically significant sense available) and so as perduring—that is, as persisting over time by virtue of having different temporal parts at different times. On my version of the tensed view, by contrast, to say that a presently existing object has persisted is just to say that that very object did exist in the past and still does so now. There is, on this view, no implication whatever that in order for this very object to have persisted until now, some other object (a temporal part of it) must have existed in the past. Notice here that, in the spatial case, it does seem intuitively right to say that a spatially extended object, such as the earth, exists now elsewhere than here (where ‘here’ refers, say, to where Durham is) by virtue of having spatial parts which now exist in other places (for instance, where San Francisco is); and the same applies, on a smaller scale, to objects like chairs. But, as I say, the verdict of the tensed view is that nothing analogous applies in the temporal case.

And, for what it is worth, I consider it to be a distinct merit of the tensed view of time that it delivers this verdict, for it surely coincides with the verdict of common sense.

This is not the end, however, of our examination of the notion of persistence and disputes over the nature and existence of temporal parts, which we shall pursue further in the next chapter. For although my own opinion is that a tensed theory of time is preferable to a tenseless theory, and that only the latter can (and must) find a place for temporal parts of persisting objects, it is possible and indeed desirable to discuss the rival

claims of endurance and perdurance theories of persistence at some remove from deeper issues concerning the nature of time itself. In fact, if I am right in believing that one's theory of time must in some measure be dictated by one's theory of persistence and vice versa, one way to defend a particular theory of time (in my own case, a tensed theory) will be to argue for a particular theory of persistence—which is what I shall be doing in the next chapter.