orthonormal comments on AI cooperation in practice - Less Wrong

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

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Comment author: RobinZ 30 July 2010 07:04:25PM *  0 points [-]

I believe Program A in "the easy version" would return 0. Assuming zero run-time errors, its structure implements the logical structure:

  • If A can be proven to return 1 in under n steps, then A returns 1.
  • If A cannot be proven to return 1 in under n steps, then A returns 0.

However n is defined (the post proposes n = 3^^^^3), it can be shown by the definition of the word "proof" that:

  • If A can be proven to return 1 in under n steps, then A returns 1.

and therefore the first proposition holds for every program, and cannot be used to show that A returns 1.

However, the second proposition also cannot be used to show that A returns 1. If the given condition holds, A does not return 1; if the given condition does not hold, the second proposition demonstrates nothing.

Therefore no property of the program can be used to demonstrate that the program must return 1. Therefore no proof can demonstrate that the program must return 1. Therefore the program will find no proof that the program returns 1. Therefore the program will return 0.

Q.E.D.

Comment author: orthonormal 31 July 2010 06:19:05PM 2 points [-]

IIRC, the modification of Gödel's statement which instead has the interpretation "I can be proved in this formal system" is called a Henkin sentence, and does in fact have a finite proof in that system. This seems weird in the intuitive sense you're talking about, but it's actually the case.

Comment author: cousin_it 31 July 2010 06:56:48PM *  1 point [-]

Yep. The Henkin sentence has already come up multiple times in the comments here. Understanding the proof of the Henkin sentence takes you about 95% of the way to understanding my original argument, I think.