Known unknowns and unknown unknowns

A lot of people made fun of poor Donald Rumsfeld for his infamous quote..

"Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know."

But actually, he had a very good point. There are things that have uncertainty but we know the shape of the uncertainty. For example, I don't know who will the lottery tomorrow, but we do know the probability of any one person winning, or the distribution of winning amounts. And by the way from that we do know that playing the lottery is one of the dumbest activities known to man, though it is a kind of stupidity that we can harness for good perhaps... but I digress. My point is the outcome of the lottery is a known unknown. Which is different type of ignorance than say, not knowing if God exists. There you don't even have a probability space to support a distribution. Once someone asked to me: What's the probability that God exists? Obviously it was a rhetorical question, and it assumed the answer is "very low" (the question came from an atheist). But then I was like: it could be 0.01% or 99.99% or anything. If you have to choose, it might as well be 42.


  1. I should note that this is the point of "Black Swan" by Taleb, which I've mentioned before. Kind of.

  2. Hey Nemo,
    Here is this piece I came across.

    Lewis's trilemma:
    In the book Mere Christianity, Lewis famously criticized the idea that Jesus was merely a human being, albeit a great moral teacher:

    I am trying here to prevent anyone saying the really foolish thing that people often say about Him: I’m ready to accept Jesus as a great moral teacher, but I don’t accept his claim to be God. That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic — on the level with the man who says he is a poached egg — or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God, or else a madman or something worse. You can shut him up for a fool, you can spit at him and kill him as a demon or you can fall at his feet and call him Lord and God, but let us not come with any patronising nonsense about his being a great human teacher. He has not left that open to us. He did not intend to. (Lewis 1952, p. 43)

    Lewis argues that Jesus made many claims to divinity, either explicitly or implicitly. As a result, he said, there are only three possible options:

    Jesus was telling falsehoods and knew it, and so he was a liar.
    Jesus was telling falsehoods but believed he was telling the truth, and so he was insane.
    Jesus was telling the truth, and so he was divine.