AlexMennen comments on Logic in the language of probability - Less Wrong

12 Post author: Stuart_Armstrong 26 April 2013 06:45PM

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Comment author: AlexMennen 27 April 2013 08:24:09PM 2 points [-]

Problem: If A is false, then A → B is true, but P(B|A) is undefined.

Comment author: Stuart_Armstrong 28 April 2013 07:33:32AM 1 point [-]

Then define by fiat that P(B|A)=1 whenever P(A)=0.

Comment author: AlexMennen 29 April 2013 01:32:25AM 2 points [-]

But then if P(A)=0, P(B|A) + P(¬B|A) = 2, which seems undesirable.

Comment author: Stuart_Armstrong 29 April 2013 07:13:02AM 1 point [-]

Since P(A|B) is properly undefined, any attempt to define it will have some negative features.