[_yb2s]

If you insist on using old fashioned logic to reason when in a probabilistic universe where that kind of reasoning is only an approximation, you can say that the universes you are talking about don't exist. They are such a small fraction of possible universes, that you can safely 'know' you aren't in any of them without checking.

[realgeniushere]

This comment misses the point and just plays with the meaning of “know”. Not that epistemology isn’t interesting, but parent was referring to absolute certainty (contingent on your senses being accurate, of course).

[skissane]

Not sure which parent you mean, but if you mean my comment, I wasn't talking about absolute certainty at all. Rather, I was attempting a reductio ad absurdum against theories which talk about the probability of different universes within a multiverse. Nothing I said is an argument against probabilistic reasoning/knowledge limited to the confines of this universe only.

[_yb2s]

I don't understand your criticism, and I think you might have been mis-understanding my intent. The Everettian (Many Worlds) interpretation of Quantum Mechanics is itself at odds with the concept of absolute certainty. I am thinking about this in terms of E. T. Jaynes perspective that probability theory is an extension of traditional logic, and is required for reasoning about the MWI.

I'll also note that I did miss the point of the OPs comment, but I think not in the way you suggested.