The Past Is Real, the Future Isn’t, and You Can’t Prove You’re Not Dead
A look at the Growing Block Theory and a new criticism
Why does time feel like it moves? Why does the past seem fixed, the present so vivid, and the future wide open? Are our intuitions about there really being a “now,” or a flow to time, on target? Or are they mistaken, such as they are when it seems to us that the sun rises and sets?
The Growing-Block Theory of Time (GBT) is an attempt to have a middle path between presentism (only the present is real) and eternalism (the past, present, and future are all equally real). In this post, I explore what the growing-block theory says, why some philosophers like it as a theory, and why others think it fails. I also sketch out a possible new concern worth considering.
What Is the Growing-Block Theory of Time?
GBT claims that both the past and present are real, but the future does not yet exist. For every present event, there is a new time-slice. I like to think of it as a loaf of bread (but any picture will do if applied properly; whatever helps you), and that loaf starts with one, very thin slice. That thin slice is “the present.” It is now. The next moment, which was future, objectively comes into existence as the present. This moves the first slice into the past. But on GBT, the slice of bread doesn’t go away. Like a real slice, it remains, and we have simply added a second slice. But then imagine the next moment comes, and we have another, and another, and so on. Time is continually growing, and events that occur in that slice are simply added to the block as time marches on. Hence, a growing block.
It has something very much in line with presentism, in that the future does not yet exist and the past is real. Slices that haven’t been added to the loaf are not present at all. But it differs from presentism in that past events do exist, and they do not go away. They will continue to build the block into the potentially infinite future. It is the same as eternalism in that it uses the idea of a four-dimensional block and treats the past and present as real; it differs from eternalism in that it denies the future is real. Eternalism needs a special note, because lay people tend not to realize that tensed language, on eternalism, is technically all reducible to tenseless statements. There is no “now” to speak of. There are only events ordered in earlier than/later than (or ‘simultaneous with’) relations. “I will go to the store in five minutes” is just shorthand for “I go to the store at 1:45pm on Thursday, and such an event stands in a later-than relation to the event of this utterance,” or something similar. GBT preserves the flow of time.
Why Would Someone Accept the Growing-Block Theory?
First, someone might be inclined to accept GBT because it fits with our intuitions of time passing. We do feel like there is an objective now and that tensed language really gets at the truth. Next, for philosophically-inclined people, it seems to solve truthmaker concerns. What makes it true that “Aristotle wrote Physics”? On GBT, it is because it is part of the block; there is something that exists in virtue of which the proposition “Aristotle wrote Physics” is true.
Third, if the future does not yet exist, then it isn’t determined. Open theists in particular may like the idea of GBT, because in their view it makes room for libertarian free will. In a theory where the future already exists, one may be tempted to think there is no human freedom, since whatever you will do already exists along the block somewhere. Thus, GBT preserves a sense of real possibility to do other than what you do at that time.
Critiques of the Growing Block Theory
I honestly like some aspects of GBT (especially because it seemingly allows for the possibility of time-travel, albeit only to the past [at least if you accept some standard accounts of the impossibility of time-travel on A-theory]). However, it is not without criticism.
First, there is the epistemic objection. Take Aristotle again. Suppose he has the belief, “GBT is real, and I am at the front-edge of the block.” In other words, he has belief that “It is now.” This is taking tense seriously, which is exactly what we intuitively want! What’s the problem? Well, time passes by. In fact, we know over 2300 years have passed since his death. He is a part of the block, located in the objective past. But since that is true, Aristotle has the now-false belief, at that exact moment along the block, that “It is now.” That is true of everyone who is not on the front-edge, in the exact present moment. On balance of probabilities, we ought to think that we are not actually in the present moment ourselves, but instead frozen in the past.
A common reply has been to say that we need to take tensed-language seriously. But this, nearly obviously to me, doesn’t solve the problem. Everyone else should have taken it seriously, too, since at some point, it was in fact true, but then became false. It doesn’t solve the problem because it doesn’t show that we are not part of that past also. Aristotle and everyone else 2300 years ago believe, at that location on the block, “It is the present,” and it’s all now false.
One promising reply is to adopt a 3D metaphysic of persons. We owe this to Ned Markosian, I believe. In other words, you don’t exist as past and present time slices along the block, but you exist wholly located in the present moment at all times. But then you might think two things: 1. We have now undercut some of the motive for the GBT (4-dimensionalism!) and 2. It means while the past exists, you are not there. And that leads to some confusing results. Basically, if you like a 3D view of persons, you might think about sticking to presentism anyway.
Second, here’s an interesting challenge I hinted at earlier. The Intentional-Object Gap is something like the following: On GBT, future selves don’t exist; nothing in the future does. Suppose you want to plan a camping trip in the future. You believe the proposition, “I will go camping next month.” On GBT, the event does not yet exist but will do so at the relevant time becoming the present moment. Intentionality requires that “I will go camping next month” is directed to or is about something that does not exist (e.g., your future self, the camping trip next month). The Intentional-Object Gap is about the space between the intention and the existence of the objects needed. So your future-directed intention should be about something, but it technically isn’t about anything existent at all. This doesn’t apply to presentists, since they can frame intentionality in terms of genuine possibilities grounded in the present (or counterfactuals). While GBT proponents can use that as well, such a move may be ad hoc; you might think that if you’re going to import presentist semantics about intentionality, then unless you absolutely need a GBT, might as well be a presentist.
So maybe you can reply with the open theist: who cares? I don’t think any such future contingents are true anyway (or they have no truth-value at all)! Fair enough. But then notice this: do intentional states require existing or realizable states in order to be formed properly? When I say “I will text you next week,” what is the proper object of that intention? My friend next week and the event of texting him do not yet exist, so how is my mental state directed at something that doesn’t exist yet?
If GBT is true, then much of our intentional life is directed at metaphysically non-existent things. Our capacity to form thoughts about things usually requires some kind of existing target (or at least a present-grounded one). If GBT must treat all future-directed thoughts as aimed at things that will become real but aren’t yet, then its account of intentionality either stands in need of a detailed account or is simply using a presentist-style grounding and semantics in possibilities and counterfactuals. In other words, just be a presentist, I say.
The Growing-Block Theory offers an attractive model: it tries to explain how time seems to pass, why the past remains real, and how the future can be open. But I think it faces serious obstacles, including the epistemological objection, that it uses presentism’s framework when it’s convenient, and my Intentional-Object Gap concern.
What do you think? Let me know in the comments!