“The rule that “absence of evidence is evidence of absence” is a special case of a more general law, which I would name Conservation of Expected Evidence: The expectation of the posterior probability, after viewing the evidence, must equal the prior probability. P(H) = P(H,E) + P(H,¬E) P(H) = P(H|E) × P(E) + P(H|¬E) × P(¬E) Therefore, for every expectation of evidence, there is an equal and opposite expectation of counterevidence.” (Eliezer Yudkowsky, Rationality)

Conservation of Expected Evidence is a good term, worth fleshing this out at some point probably.