I dealt with this objection in the second article of the series. It would be easy to say that there are two simulations, in which slightly different things are going to happen.

While this is also a valid and interesting scenario to consider, I don't think it "deals with the objection". The idea that "which computer am I running on?" is a meaningful question for someone whose experiences have multiple encodings in an environment seems pretty central to the discussion.

Does this mean that if we had a billion identical simulations of you in a VR where you were about to see a red ball and one (different) simulation of you in a VR where you are about to see a blue ball, and all these were running on separate computers, and you did not know which situation you were in, you would not think it more likely you were going to see a red ball?

I actually don't have a good answer to this, and the flavor of my confusion leads me to suspect the definitions involved. I think the word "you" in this context denotes something of an unnatural category. To consider the question of anticipating different experiences, I have to assume a specific self exists prior to copying. Are the subsequent experiences of the copies "mine" relative to this self? If so, then it is certain that "I" will experience both drawing a red ball and drawing a blue ball, and the question seems meaningless. I feel that I may be missing a simple counter-example here.

I know a common answer here is that it is still 50/50 - that copies don't count - which I can answer if you say that and which is addressed in the second article

50/50 makes sense to me only as far it represents a default state of belief about a pair of mutually exclusive possibilities in the absence of any relevant information, but the exclusivity troubles me. I read objection 9, and I'm not bothered by the "strange" conclusion of sensitivity to minor alterations (perhaps this leads to contradictions elsewhere that I haven't perceived?). I agree that counting algorithms is just a dressed-up version of counting machines, because the entire question is predicated on the algorithms being subjectively isomorphic (they're only different in that some underlying physical or virtual machine is behaving differently to encode the same experience).

Of course, this leads to the problem of interpretation, which suggests to me that "information" and "algorithm" may be ill-defined concepts except in terms of one another. This is why I think I/O is important, because a mind may depend on a subjective environment to function. If this is the case, removal of the environment is basically removal of the mind. A mind of this sort, subjectively dependent on its own substrate, can be "destroyed" relative to observers of the environment, as they now have evidence for the following reasoning:

• Mind M cannot logically exist except as self-observably embedded in environment E. So if E lacks such an encoding, M cannot exist.
• I have observed E, and have sound reasons (local to E) to doubt the existence of a suitable encoding of M.
• Therefore, M does not exist.

So far, this is the only substrate dependence argument I find convincing, but it requires the explicit dependence of M on E, which requires I/O.