If the same computation is being run in so-called 'basement reality' and run on a simulator's computer, you're in both places; it's meaningless to talk about the probability of being in one or the other.
Why meaningless? It seems I can talk about one copy of me being here, now, and one copy of myself being off in the future in a simulation. Perhaps I do not know which one I am, but I don't think I am saying something meaningless to assert that I (this copy of me that you hear speaking) am the one in basement reality, and hence that no one in any reality knows in advance that I am about to close this sentence with a hash mark#
I'm not asking you to bear the burden of proving that non-basement versions are numerous. I'm asking you to justify your claim that when I use the word "I" in this universe, it is meaningless to say that I'm not talking about the fellow saying "I" in a simulation and that he is not talking (in part) about me. Surely "I" can be interpreted to mean the local instance.
Both copies will do exactly the same thing, right down to their thoughts, right? So to them, what does it matter which one they are? It isn't just that given that they have no way to test, this means they'll never know, it's more fundamental than that. It's kinda like how if there's an invisible, immaterial dragon in your garage, there might as well not be a dragon there at all, right? If there's no way, even in principle, to tell the difference between the two states, there might as well not be any difference at all.
Please read the post before voting on the comments, as this is a game where voting works differently.
Warning: the comments section of this post will look odd. The most reasonable comments will have lots of negative karma. Do not be alarmed, it's all part of the plan. In order to participate in this game you should disable any viewing threshold for negatively voted comments.
Here's an irrationalist game meant to quickly collect a pool of controversial ideas for people to debate and assess. It kinda relies on people being honest and not being nitpickers, but it might be fun.
Write a comment reply to this post describing a belief you think has a reasonable chance of being true relative to the the beliefs of other Less Wrong folk. Jot down a proposition and a rough probability estimate or qualitative description, like 'fairly confident'.
Example (not my true belief): "The U.S. government was directly responsible for financing the September 11th terrorist attacks. Very confident. (~95%)."
If you post a belief, you have to vote on the beliefs of all other comments. Voting works like this: if you basically agree with the comment, vote the comment down. If you basically disagree with the comment, vote the comment up. What 'basically' means here is intuitive; instead of using a precise mathy scoring system, just make a guess. In my view, if their stated probability is 99.9% and your degree of belief is 90%, that merits an upvote: it's a pretty big difference of opinion. If they're at 99.9% and you're at 99.5%, it could go either way. If you're genuinely unsure whether or not you basically agree with them, you can pass on voting (but try not to). Vote up if you think they are either overconfident or underconfident in their belief: any disagreement is valid disagreement.
That's the spirit of the game, but some more qualifications and rules follow.
If the proposition in a comment isn't incredibly precise, use your best interpretation. If you really have to pick nits for whatever reason, say so in a comment reply.
The more upvotes you get, the more irrational Less Wrong perceives your belief to be. Which means that if you have a large amount of Less Wrong karma and can still get lots of upvotes on your crazy beliefs then you will get lots of smart people to take your weird ideas a little more seriously.
Some poor soul is going to come along and post "I believe in God". Don't pick nits and say "Well in a a Tegmark multiverse there is definitely a universe exactly like ours where some sort of god rules over us..." and downvote it. That's cheating. You better upvote the guy. For just this post, get over your desire to upvote rationality. For this game, we reward perceived irrationality.
Try to be precise in your propositions. Saying "I believe in God. 99% sure." isn't informative because we don't quite know which God you're talking about. A deist god? The Christian God? Jewish?
Y'all know this already, but just a reminder: preferences ain't beliefs. Downvote preferences disguised as beliefs. Beliefs that include the word "should" are are almost always imprecise: avoid them.
Additional rules: