Gödel proved that there are true sentences that cannot be proved.
Suppose I told you that the Goldbach conjecture is one of those. (The Goldbach conjecture supposes that every even integer number can be expressed as the sum of two odd primes.)
Is that logically possible? (And, no, I haven't proved it!)
(In reply to Waiting for Godel (Spoiler)
Yes, that was interesting. I never heard of the Goldbach Conjecture, Godel, Peano arithmatic or symbols (thank you Penny) until I read this puzzle. At least not that I can recall. My question is, What does ZF refer to in the comment you posted?