Or to put it another way, the world isn't deterministic. A and not-A aren't the only options; there's also "sometimes A, sometimes not-A, depending on where in

Or to put it another way, the world isn't deterministic. A and not-A aren't the only options; there's also "sometimes A, sometimes not-A, depending on where in the probability distribution each situation falls". And here's where we need to distinguish knowledge of evidence from evidence itself; if you haven't collected any observations, then not knowing of any evidence doesn't imply that evidence is actually absent. In other words, "I don't know" isn't actually absence of evidence.