[roywiggins]

This is a good way to solve problems in NP. First, guess an answer uniformly at random. Check if it's correct (in polynomial time). If it isn't, blow up the planet. Conditioned on surviving, you also have solved the NP problem in polynomial time.

You can also use a world-ending device to prove that this reasoning works. Blow up the world with probability .99999999999. Conditioned on surviving, you will then be nearly certain that quantum hell is real- more certain than about nearly any other physical theory.

The other problem is that depending on how you count, almost all observers are actually hallucinating Boltzmann brains. There are duplicates of us, but there are arguably even more pocket universes with hallucinating brains that just very briefly remember being something like us and then die.

So that's not very reassuring.