Tuesday, March 27, 2007

The Shrinking Block

Why are there no defenders of the shrinking block theory of time - the view that the present and future exist but not the past? Here's one advantage of the theory: it gives a good explanation for a version of the 'thank goodness that's over' intuition. If I tell you that there is going to be an hour of pain in your lifetime and you can choose whether it's to be in your past or your future which would you choose? I bet, other things' being equal, you'd choose it to be in your past. But why? If Shrinking Block is true there's a good reason for so choosing: existent pains are a lot worse than non-existent ones.

Does Growing Block have advantages over Shrinking Block? Why be a growing block theorist? My old friend from grad school, Joseph Diekemper (currently Gifford fellow at St Andrews, and soon to be lecturer at Queen's Belfast) cites the fixity of the past and the openness of the future as reason to accept Growing Block. But his main target is the presentist: Joseph thinks the presentist can't account for the asymmetry in fixity because they have no corresponding asymmetry between the past and future. Well, this alone won't move the Shrinking Block theorist, because they do have such an asymmetry - it's just the other way around from the Growing Block.

Indeed, in some ways the Shrinking Block view seems more able to account for the fixity of the past and the openness of the future. The intuition to be saved, I take it, is that we can affect how the future will be but not how the past was. Well ask yourself this: what would it be easier for us to affect - an existent state of affairs or a non-existent one? Surely an existent one, since we can't even have causal interaction with a non-existent state of affairs.

I'm not seriously trying to get you to believe the Shrinking Block theory, of course. But I'd be interested to know just why Growing Block is meant to be a better option.


Jonathan said...

Hi Ross,

Here's a stab at such a reason: one of our pre-theoretical notions seems to be that the present is real (it's where it's all at), the past is kinda real (you know, it's better than the future, but not quite as real as the present) and the future isn't real.
Because the intuition is that the past is 'more real' than the future it would make sense to run with a Growing Block than a Shrinking block.
That's not a great reason, but it leads into intuitions about truths, too. If you're a growing blocker you can claim to have truth-makers for truths about the past, though you might well lack them for truths about the future. Now that seems right. At least, it seems *better* than saying that we have truths about the future and not the past.
There are obviously ways around this, but I think that might go some way to explaining the intuitive pull of the growing block that isn't available to the proponent of shrinking block.



Andrew Jorgensen said...

Hi Ross,

Something I've wondered about these sorts of questions, is how they cohere with the intuition that nothing comes from nothing. If time is to be likened to a growing block, and the present and the past are both real, that seems to entail that there's more and more of reality (it's a growing block). But where does all the extra reality that becomes the present with each passing moment come from? If the future isn't also real then it must come from nowhere, which conflicts with the intuition. And the same thing seems to count against the shrinking block theory. How can things just cease to exist? How could there be, say, five parts of reality one day and then four the next? That would sort of impugn the reality of the real, if it could just disappear.
What do people say about this sort of thing?

Enigman said...

Seems reasonable. So presumably the past is as real as the present, just less accessible (to people like ourselves). And although we can affect the future, given indeterminism, that seems to be only in the sense of affecting the possibilities for what will be present, for what will have happened (rather than some weird transtemporal affecting of a distant future). Maybe the past is as real as the present, but is vacant rather than occupied by people affecting what will have happened?

Enigman said...

That is, I feel that we don't so much get a present world where there was nothing = the future, so much as involve ourselves in the picking out of one of the possibilities to be actual; not so much getting extra reality as relabelling stuff, or perhaps compressing multiple possibilities into single actualities?

Enigman said...

Anyway, I think that is why we think of the past as real, like the present. We are interested in the future because it will be real (so to speak) not because it is real (although it contains real enough possibilities). After all, science tells us that the ordinary objects around us (which are paradigmatically real) are experienced as they were, slightly in the past. So maybe serious defenders of the shrinking block theory of time would have to experience the future possibilities directly, before they drop off the prescients' radars by actualising into the present and past... and that is so unlike ourselves that I even doubt its conceivability.

Andrew Jorgensen said...

I thought the bearing of the 'nothing comes from nothing' idea was that it suggests a kind of "conservation of reality" idea. There can't be changes in the amount of stuff that's real. There would be changes if the past was real but the future wasn't, in the growing block case, and vice versa, in the shrinking case. So, either neither the past nor the future is real or both of them are. If they were both real, there couldn't be many possible tomorrows but only one yesterday, because that would involve a kind of shrinkage too (from many down to one), so if any of the future is real and there's only one past, there can be only one future.

Enigman said...

Yes, but there are numerous possible equivocations with words like 'real'. Possibilities can be real, for if physical indeterminism is the case then there are real possibilities in the future (not just fictional ones). Cf. how matter can disappear, so long as the total energy is conserved; so when by 'real' is meant a basic ontological resemblance to the ordinary objects around us, then there is little force behind the idea that it is a conserved quantity (not to mention problems with summation, e.g. if a cup breaks do we have more things?)...

Anonymous said...

Here's a video that comes at the issue from a somewhat different angle, but makes the case that the shrinking block view is worth a closer look: http://www.youtube.com/watch?v=IC6cP0fvmuw