There Are Aliens, but Probably Not Here
This article makes a familiar error in thinking that I routinely see when it comes to the subject of extraterrestrial life. It goes like this:<p>1) There exist billions and billions of stars, each of which can be thought of an independent Bernoulli trial with probability P as to whether intelligent life exists in that star system.<p>2) P must be a non-negligible quantity, because we ourselves exist<p>3) Therefore intelligent life &quot;must&quot; exist elsewhere in the universe due to the sheer number of trials.<p>This is an epistemological error that echoes the sort of error made by proponents of intelligent design. They conclude that the chance of thinking beings evolving is prodigiously unlikely, and therefore our existence is proof of a creator.<p>But in fact, you cannot post-hoc conclude that our existence says anything at all about P, because if we didn&#x27;t exist, there would be no one to ask the question. Therefore the fact that we are wondering about the value of P means our existence is an implicit axiom of the logical system itself. One way to think of it is there could be infinitely many possible universes with no life at all, and by definition the question of P can only discussed in the one branch, in all that lifeless space of possibilities, where thinking beings actually exist. So P could, in fact, be made arbitrarily small, and Earth could indeed be the only place in the universe with intelligent life.<p>Note that this doesn&#x27;t claim that extraterrestrial life _doesn&#x27;t_ exist. It merely points out the truth in all of this P-hacking: that we have no evidentiary basis for believing one way or the other.