This is one of two ways I know of proving Löb's theorem, and I find them both illuminating. (The other is to derive it from Gödel's Second Incompleteness Theorem.)

by Patrick LaVictoire Jul 21 2016

This is one of two ways I know of proving Löb's theorem, and I find them both illuminating. (The other is to derive it from Gödel's Second Incompleteness Theorem.)