You would not think it, to look at them. There is no a priori probability about it. A strange enigma is man!
只看他们的外表，你是想不到的。这并不是先天的，人生就是一个谜。
英语百科
A priori probability
（重定向自Priori probability）
An a priori probability is a probability that is derived purely by deductive reasoning. One way of deriving a priori probabilities is the principle of indifference, which has the character of saying that, if there are N mutually exclusive and exhaustive events and if they are equally likely, then the probability of a given event occurring is 1/N. Similarly the probability of one of a given collection of K events is K/N.