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Allan_Crossman comments on The Cartoon Guide to Löb's Theorem - Less Wrong

12 Post author: Eliezer_Yudkowsky 17 August 2008 08:35PM

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Comment author: Allan_Crossman 18 August 2008 02:53:16AM 0 points [-]

Boiling it down to essentials, it looks to me like the key move is this:

  • If we can prove X, then we can prove Y.
  • Therefore, if X is true, then we can prove Y.

But this doesn't follow - X could be true but not provable.

Is that right? It's ages since I did logic, and never to a deep level, so excuse me if this is way off.