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 01 August 2010 10:20:13AM *  2 points [-]

What you're saying is certainly true (onlookers, see pages 5-6 of this pdf for as especially clear explanation), but I like to think that you can't actually exhibit a proof string that shows the inconsistency of PA. If you could, we'd all be screwed!

Comment author: Vladimir_Nesov 01 August 2010 10:39:17AM 0 points [-]

I like to think that you can't actually exhibit a proof string that shows the inconsistency of PA.

Proof in what theory, "can't" by what definition of truth? In the extension of PA with inconsistency-of-PA axiom, it's both provable and true that PA is inconsistent.

Comment author: cousin_it 01 August 2010 10:44:36AM 1 point [-]

A proof in PA that 1+1=3 would suffice. Or, if you will, the Goedel number of this proof: an integer that satisfies some equations expressible in ordinary arithmetic. I agree that there's something Platonic about the belief that a system of equations either has or doesn't have an integer solution, but I'm not willing to give up that small degree of Platonism, I guess.

Comment author: Vladimir_Nesov 01 August 2010 10:56:24AM 0 points [-]

You would demand that particular proof, but why? PA+~Con(PA) doesn't need such eccentricities. You already believe Con(PA), so you can't start from ~Con(PA) as an axiom. Something in your mind makes that choice.