cousin_it comments on AI cooperation in practice - Less Wrong

26 Post author: cousin_it 30 July 2010 04:21PM

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Comment author: cousin_it 31 July 2010 07:38:55PM *  4 points [-]

can't you prove that proves(outputs(2), n) implies the negation of proves(outputs(1), n)

To prove that, the proof system would need to know its own consistency, because an inconsistent proof system could prove both of these statements and indeed any statement at all. But a proof system cannot know its own consistency without actually being inconsistent (Goedel's second theorem).

Comment author: Vladimir_Nesov 31 July 2010 08:30:53PM *  1 point [-]

For a finite set of proofs, that a given statement is not provable by a proof from that set, is provable, possibly by a proof from that set.

Comment author: cousin_it 31 July 2010 09:14:30PM *  2 points [-]

Technically true. You could always just evaluate the two statements and there you have your proof, with length exponential in n. I very much doubt the proof could be made shorter than n though, because the statement is equivalent to "you can't find a contradiction in these axioms using less than n steps", the difficulty of which should grow way faster than linearly in n.

Comment author: AlephNeil 31 July 2010 07:41:38PM 0 points [-]

Aha - very cunning.