A Proof that Pr(H|E) > Pr(H) entails Pr(H|E) > Pr(H|~E)
A proof for the following conditional: Pr(H|E) > Pr(H) only if Pr(H|E) > Pr(H|~E).
- P(H|E) > P(H)
- P(H|E) > P(H) iff P(E|H) > P(E|~H) [Mackie's relevance criterion].
- P(E|H) > P(E|~H) [MP, 1 & 2].
- P(~E|H) = 1 - P(E|H) [subtraction].
- P(~E|~H) = 1 - P(E|~H) [subtraction].
- [1 - P(E|~H)] > [1 - P(E|H)] [from 3].
- P(~E|~H) > P(~E|H) [from 4, 5, & 6].
- P(H) > P(H|~E) iff P(~E|~H) > P(~E|H) [premise].
- P(H) > P(H|~E) [MP, 7 & 8].
- P(H|E) > P(H) > P(H|~E) [from (1), (9)].
- P(H|E) > P(H|~E) [from 10].
- Therefore, P(H|E) > P(H) only if P(H|E) > P(H|~E).
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