Considering all the layers of convention and interpretation between the physics of a processor and the process it represents, it seems unlikely to me that the alien would be able to describe the simulacra. The alien is therefore unable to specify the experience being created by the cluster.
I don’t think this follows. Perhaps the same calculation could simulate different real world phenomena, but it doesn’t follow that the subjective experiences are different in each case.
If computation is this arbitrary, we have the flexibility to interpret any physical system, be it a wall, a rock, or a bag of popcorn, as implementing any program. And any program means any experience. All objects are experiencing everything everywhere all at once.
Afaik this might be true. We have no way of finding out whether the rock does or does not have conscious experience. The relevant experiences to us are those that are connected to the ability to communicate or interact with the environment, such as the experiences associated with the global workspace in human brains (which seems to control memory/communication); experiences that may be associated with other neural impulses, or with fluid dynamics in the blood vessels or whatever, don’t affect anything.
Could both of them be right? No—from your point of view, at least one of them must be wrong. There is one correct answer, the experience you are having.
This also does not follow. Both experiences could happen in the same brain. You—being experience A—may not be aware of experience B—but that does not mean that experience B does not exist.
(edited to merge in other comments which I then deleted)
The argument presented by Aaronson is that, since it would take as much computation to convert the rock/waterfall computation into a usable computation as it would be to just do the usable computation directly, the rock/waterfall isn’t really doing the computation.
I find this argument unconvincing, as we are talking about a possible internal property here, and not about the external relation with the rest of the world (which we already agree is useless).
(edit: whoops missed an ‘un’ in “unconvincing”)