The Devil Proof

"The Devil's in the details."

"The proof's in the pudding."

I've heard these things a lot recently and they've gotten me thinking about their meanings. Why are these "negative" things the things we seek?

I should say, I don't know if they are negative in fact, but they seem so.

Details are a good thing, and I suppose the Devil being in them might indicate something negative. It's a hardship, or at least something that might bring along unpleasantness.

The proof might be another negative thing, something one might not want in the final product of the pudding.

I don't know, but I should look these up to see if my thoughts are worth anything.