Good Entropy

Jaynes used to recommend that no one ever write out an unconditional probability: That you never, ever write simply P(A), but always write P(A|I), where I is your prior information. I’ll use Q instead of I, for ease of reading, but Jaynes used I. Similarly, one would not write P(A|B) for the posterior probability of A given that we learn B, but rather P(A|B,Q), the probability of A given that we learn B and had background information Q.

This is good advice in a purely pragmatic sense, when you see how many false “paradoxes” are generated by accidentally using different prior information in different places.

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Probability is Subjectively Objective