Should I somehow try to assess my likelihood of meeting Omega (in some form or other) and guess what sort of parlour game it is likely to play with me, and for what stakes? Has anyone got any idea how to do that assessment, without unduly privileging the games that we happen to have thought of so far? This way madness lies I fear...
Not exactly madness, but Pascal’s wager. If you haven’t seen any evidence of Omega existing by now, nor any theory behind how predictions such as his could be possible, and word of his parlour game preferences has not reached you, then chances are that he is so unlikely in this universe that he is in the same category as Pascal’s wager.
I’m way late to this party, but aren’t we ignoring something obvious? Such as imperfect knowledge of how likely Omega is to be right about its prediction of what you would do? If you live in a universe where Omega is a known fact and nobody thinks themselves insane when they meet him, well, then it’s the degenerate case where you are 100% certain that Omega predicts correctly. If you lived in such a universe presumably you would know it, and everyone in that world would pre-commit to giving Omega $100, just like in ours pizza-deliverers pre-commit to not carrying more than a small amount of cash with them.
There may be other universes where Omega is known to be right and do what he says he will do 80% of the time. Or ones where there are rumors of an omniscient Omega that always makes good on his word, but you assign them 80% probability of being true. And so on.
Given the $5000 expected payoff and the $50 expected cost for pre committing, you should do it if the probability of Omega being both right and trustworthy is greater than or equal to 0.01.
But, if you, knowing what you know about THIS universe, suddenly found yourself in the presence of some alien entity making the claim Omega makes in the above scenario, what kind of evidence would you demand for this claim before assigning a probability greater than 0.01?
It occurs to me that the dude in the robe and mask pretending to be Omega could up the ante to $1000000, and if I wouldn’t believe him more than 0.01% given a $10000 payoff, it probably wouldn’t matter to me what he offered as a payoff, because if he has enough delusions and/or chutzpah to make this claim in this universe, there’s no reason for him to balk at adding on a few extra decimal places. I’m not sure how to formalize that mathematically, though.