Imagine a Life universe that contains, among other things, two SASes talking to each other (and showing each other pictures, and in general having a very lucid, conscious, conversation.) Imagine that instead of being implemented on a computer, it's implemented by a large 2d array of coins: heads represents "live", and tails represents "dead". Each timestep, the coins are flipped over in concordance with the Life rules.
Does this setup implement a universe?
If you say it does, how about the next step:
Instead of doing flipping operations on one set of coins, each new generation is laid down in the proper configuration on top of the preceding one with a new set of coins. Does this >process< of laying down coins also implement a universe?
If you say it does, then what about the stack itself? (One can imagine pointing to each layer in succession, saying "This is the current step", "Now this is the current step", etc..) Does the stack's bare existence suffice for the implementation of a universe?
If not, then can you say what it is about the active process of flipping or laying down that "counts" as computation but does not count when the stack is a static block?
If you think the static block "counts" as the implementation of a universe, then I think you can go all the way to abstract Platonism. Because since the stack's just sitting there, why not knock it down? Or melt it into a big ball? Or throw it into a black hole...the two SASes won't care (will they?)
So I think the anti-Platonist must answer why exactly the coins need to be actively flipped or laid down to "really" implement a Life universe -- and by extension, why any universe needs to be "actively" implemented.
Then question then becomes, I suppose, if in fact our universe is a digital
one (if not strictly a CA) havng self-consistent emergent physics, then
might it not follow that it is "implemented" (run?) via some extra-universal
physical processes that only indirectly correspond to ours?
(if the above is too painfully obvious (or goofy?) and/or old news then,
again, do humor me..)