Manfred comments on Walkthrough of "Definability of Truth in Probabilistic Logic" - Less Wrong

11 Post author: So8res 09 December 2013 03:44AM

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Comment author: Manfred 09 December 2013 05:01:00AM *  0 points [-]

The empty set is tautological because P({}) = P({} and something) + P({} and not-something) = P(something) + P(not-something). Hm, but that's using axioms 1 and 2. Can we get it using just axiom 3 as the paper claims?

Comment author: benkuhn 09 December 2013 08:36:07AM 1 point [-]

When you say that P({} and something) = P(something), you suppose the hypothesis (in addition to using several nontrivial consequences of coherence that So8res mentioned, like P mapping equivalent statements to the same thing).

More importantly, "{} and something" isn't a syntactically correct sentence. I don't think most authors consider the empty sentence syntactically correct either. (Marker, the textbook I used, doesn't.)

Comment author: Manfred 09 December 2013 06:58:21PM 0 points [-]

Whoops, you're right.