Thursday, October 19, 2023

Two implications of Aristotle's theory of time and locality

Aristotle thinks that time is infinitely subdivisible but only finitely subdivided. Thus, there will be moments t1 < t2 such that there is actually no moment between t1 and t2, but there could have been. What would make there have been a moment between t1 and t2? Presumably, this would be if something happened strictly between those times. Time is the measure of change, so if, say, some object started or finished changing at a time between t1 and t2, then there would have been a time between them, say t1.5.

But here is a curious consequence. Suppose that in the actual world, w0, I am living from t1 to t2, which are so close together in time that there are no time between them. But in another world, t1, where everything in our galaxy was the same, in some other galaxy indeterministically an event happened between t1 and t2, namely at t1.5. Then:

  • In w0, it is not true that I exist at t1.5 (because there is no t1.5).

  • In w1, it is true that I exist at t1.5.

And what is responsible for that difference is that indeterministic event in another galaxy. So it seems that something in another galaxy is responsible, in a faster-than-light way, for whether I exist at t1.5. In other words, the Aristotelian theory seems to imply highly non-local influences.

There is perhaps a way out. Perhaps fundamentally time sequences are internal to substances. Thus, I have a time sequence internal to me, you have one internal to you, and things in that other galaxy have time sequences internal to them. There are, additionally, connections (probably causal ones) between objects that allow one to form a global time sequence. That global time sequence will include moments that don’t correspond to any moments internal to me. For instance, it will include moments earlier than my conception, but more interestingly, it could be that for me t2 immediately succeeds t1, but something else has a time that fits between t1 and t2, and so global time could have times corresponding to t1 and t2, but also some intermediate time between them.

The difference between w0 and w1, then, would not be a difference in my internal time sequence. What happened in that other galaxy wouldn’t affect my internal time except perhaps once the light from that galaxy could reach me.

On this account, while it is true that I exist at t1.5, my existing at t1.5 is not an intrinsic feature of me. The difference between my existing at t1.5 in w1 and my not existing at t1.5 in w0 is a merely Cambridge difference.

I think it is hard to make this story fit with presentism. When t1.5 is present, then it had better be intrinsic to me that I exist presently, i.e., at t1.5. A similar point applies to growing block.

Maybe, though, there is a way of making this story fit with a moving spotlight A-theory. We could suppose that at global time t1.5, what is “lit up” by the spotlight is the time t1.5 for the thing in the other galaxy that has something happening to it then, but for me what is lit up is the entire interval between t1 and t2.

If I am right, then

  1. Locality, and

  2. Aristotle’s theory of time

seem to imply:

  1. Internal time is primary

  2. Eternalism is true.

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