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JoshuaZ comments on [LINK] Steven Landsburg "Accounting for Numbers" - response to EY's "Logical Pinpointing" - Less Wrong Discussion

9 Post author: David_Gerard 14 November 2012 12:55PM

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Comment author: JoshuaZ 16 November 2012 04:10:53AM 1 point [-]

I think there's a definitional issue here. Eugine is using "proof checker" to mean an algorithm that given a sequence of statements in an axiomatic system verifies that the proof is formally valid. You seem to mean by proof checker something like a process that goes through listing all valid statements in the system along with a proof of the statement.

Comment author: StevenLandsburg 16 November 2012 12:54:34PM 0 points [-]

JoshuaZ: No, I mean the former. The problem is that you have enough rules of inference to allow you to extract all logical consequences of your axioms, then that set of rules of inference is going to be too complicated to explain to any computer. (i.e. the rules of inference are non-recursive.)

Comment author: JoshuaZ 16 November 2012 01:43:58PM 1 point [-]

Isn't that more a consequence of the stronger statement that you just can't write down all valid inferences in the second-order system?