Related: I have always considered that the chance of finding life (or intelligent life) is unknown, because unless we don't find a second data point (first bein

Related: I have always considered that the chance of finding life (or intelligent life) is unknown, because unless we don't find a second data point (first being us) it is not possible to estimate how common or rare it is. We can talk all we want about filters and stages to intelligent life, but it doesn't really mean anything until a 2nd case is observed.