Hacker News Reader

If I haven't looked in my desk drawer, this is not evidence that it's empty. It's only evidence that it's empty if I open it and don't see anything.

Or, put another way: The real world isn't boolean. A and Not-A are not the only options; there's also "I don't know."

The last case there is what's generally referred to when people say that absence of evidence is not evidence of absence.

View on HN

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.

Also known as criticisms of the Law of Excluded Middle.

Reply on news.ycombinator.com