Friday, October 20, 2023

Wacky reality dynamics

The dynamics of reality over time vary between theories of time. On growing block, at each moment a new present slice is added to reality. On presentism, at each moment the formerly present slice is subtracted from reality and a new present slice is added to replace it.

But once we admit that there are at least these two such “reality dynamics”, other possibilities show up.

Centisecondism: At each moment, the slice one millisecond (i.e., 0.01 seconds) in the past (if there is one) is subtracted from reality, while a new present slice is added. As a result, except during an initial one centisecond warmup when reality is just growing, reality is always a one-centisecond thick chunk. Centisecondism is superior to presentism in multiple ways. First, it seems hard to fit consciousness in an infinitesimally long reality, as in presentism, but a centisecond is good enough. Second, a centisecond is long enough for diachronic causal relations to be unproblematic. Third, presentism suffers from the problem that on presentism we never see reality. Because of light-travel times, we always see the past, and the past is not real! On centisecondism, we have a chance to see reality as it is.

Of course, a centisecond is arbitrary. The actual slice thickness could be bigger or smaller. It may seem ad hoc what it is. But it’s no more ad hoc than, say, the fine structure constant or any other constant in the laws of nature. If there is a God, he can decide on the slice thickness, in his wisdom, just as he decides on the fine structure constant. If there is no God, the thickness constant can be brute.

Eschatological growing block: Presentism is true right now: reality is one-moment thick. But then comes an eschaton. At the eschaton, suddenly all those past slices that had disappeared due to presentism pop back into reality, and we stop subtracting from reality, and begin to just add. Now we have growing block. This could give us a kind of transcendent outlook on the past in the eschaton. The eschatological growing block has the interesting consequence that being-real-at is not a symmetric relation. For instance, the time of the eschaton is not real at 2023, but 2023 is real at the time of the eschaton. This may seem strange, but in fact is true on any growing block theory.

Eschatological eternalism: Presentism is true right now. But eternalism starts to be true at the eschaton—at the eschaton not just one moment, and not just the past, but the whole past, present and future pop into reality. This provides a kind of temporalized version of Leftow’s model of a timeless God’s relation to a presentism time—the beings in the eschaton have an eternalist relation to our presentist time.

One might think that these theories require hypertime. That is not true for centisecondism or eschatological growing block, because centisecondism and eschatological growing block have room for defining the present moment without moving to hypertime. The present moment on both theories is just the leading the edge of reality. On eschatological eternalism, if we could get in a moving spotlight, then we could define a present moment. (Or could we have an eschatological eternalism on which “at the eschaton” all the “past, present and future” are actually present?)

I think centisecondism and eschatological growing block are both coherent if standard growing block is coherent. If I were a growing blocker, I think I would think that God could make a world where presentism or centisecondism or eschatological growing block are true, or almost true (by that I mean that in those worlds there wouldn’t be time, but time*).

But I am B-theorist eternalist, and I am just giving all these stories for fun. I suspect that they are all ultimately impossible, as are presentism (of a standard sort) and growing block.

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