Epistemology for Time-Travelers

Epistemology for Time-Travelers February 2, 2012

I’ve been mulling over a weird thought-experiment, and I’d be really interested in your intuitions.  (I’ll explain why I’ve been thinking about it in a subsequent post).

Poof! In a burst of special effects, you’re confronted by a doppleganger you!

“Hi,” other!you says, “I’m you from the future.”  Future!you knows enough about you that you’re convinced it is indeed you, and does something that makes it probably s/he is really from the future (predicts a couple events).

“Wow,” you say, “my mind has been blown.”

“You shouldn’t speak so fast,” says future!you.  “I should tell you I’ve also converted to [not your current religious beliefs].”

After reviving you with smelling salts from the future, the new you says, “Look, I can’t tell you the exact reasons I changed my mind (it’s a timey-wimey restriction) but I’m glad to talk epistemology with you until you agree that we have the same threshold for evidence on this question.”

Should knowing that future!you has been persuaded be enough to persuade you?

Does the very fact of a conversion eliminate your confidence in future!you’s rationality?   What kind of things would you still have to agree on in order to believe that what persuades them would persuade you?

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