4 ms·

There's also Godel's completeness theorem for first order logic. Much easier to prove, and also extremely important.

• lmm 10y ago
  Not Goedel's, is it? I thought that was known long before him.
  • jesuslop 10y ago
    he's right, it was Gödel's.
• pron 10y ago
  It's one of the foundations of model theory.