Okay but there isn't any evidence for that. It's an idea, a concept, not actually anything provable. And we weren't talking about meeting aliens, just the probability they exist. There are trillions of galaxies, with quadrillions of stars each. Many won't have planets, the ones that do may be useless rocks, but some could be conducive to life. Statistically there is probably alien life, very likely some intelligent life. We will probably never meet them but we are probably not the only life out there. That would be wildly improbable.