"there is the small matter of the matter the computer is made of"
Well yes he did indeed mention that. But does it have to be made of matter at all? There are lots of delicious possibilities.
One possibility is that it could be being simulated by some yet higher level of universe. And that higher level? Could be being simulated by some yet higher level still. Does this chain of recursive simulations ever have to end up with an actual top level simulator made of matter? Maybe there is no top level, and *every* level is simulated by some yet higher level.
Numbers go on for ever. There doesn't have to be a biggest number. Every number nestles comfortably in the shadow of a bigger number. Likewise, every universe could be sweetly simulated by a higher universe.
Psychedelic and unconvincing, you say? Also, one might add, a tad over-complicated? Well, psychedelic is good, no problem with that.
As for the unconvincingness and the complicatedness, I think that what trumps both of those is the amazing *economy* of such a scheme.
Because, the problem with a material universe is that it is so darned expensive. All that stuff, all those bits and pieces, where do they all come from, who paid for them? Each particle could be pretty small, but add them all up and they must weigh tons.
A stack of simulating universes, none of which are actually made of matter, would be cheap and light.
I think Mr G might have been hinting along these lines when he said "if all particles of matter can be described digitally, as well as the laws that govern their interactions, it means that we don't really need matter at all."
Or maybe he was going even further, and suggesting that a simulated universe would be so lightweight and maintenance-free (after all, the parts wouldn't even need oiling) that perhaps it wouldn't even need a simulator ... it could just ... kind of ... be.
In which case, have we actually said anything at all?
This is where Wittgenstein comes in.