Paul_Gowder comments on Infinite Certainty - Less Wrong

32 Post author: Eliezer_Yudkowsky 09 January 2008 06:49AM

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Comment author: Paul_Gowder 09 January 2008 08:13:52AM 7 points [-]

We can go even stronger than mathematical truths. How about the following statement?

~(P &~P)

I think it's safe to say that if anything is true, that statement (the flipping law of non-contradiction) is true. And it's the precondition for any other knowledge (for no other reason than if you deny it, you can prove anything). I mean, there are logics that permit contradictions, but then you're in a space that's completely alien to normal reasoning.

So that's *lots* stronger than 2+2=4. You can reason without 2+2=4. Maybe not very well, but you can do it.

So Eliezer, do you have a probability of 1 in the law of non-contradiction?

Comment author: sullyj3 10 July 2016 04:15:56AM 0 points [-]

The truth of probability theory itself depends on non-contradiction, so I don't really think that probability is a valid framework for reasoning about the truth of fundamental logic, because if logic is suspect probability itself becomes suspect.