Hmm... I'm not sure if I think of myself as an expert at anything, other than when people ask. But I'm pretty sure I have about the best understanding of logic I can hope to have, and could explain virtually all of it to an attentive small child given sufficient time.

And I might be an expert at some sort of computer programming, though I can think of people much better at any bit of it that I can think of; at any rate, I am also confident I could teach that to anyone, or at least anyone who passes a basic test