How Many Intelligent Civilizations Are Out There?

Setti is a way of organizing our ignorance, it's basically a gestimation technique. It divides up how many intelligent civilizations might we find into a series of conditional probabilities. And the important thing is that if any of those factors are completely unconstrained, then you really can't calculate anything. If i told you an answer to that equation, if i told you a number, it would be more like religion than science.