True, and I boggle at the possible variations on probabilities and numbers involved. (I'm quite surprised at scientists who do try to put numbers on it.)

I suspect that all the SF I've read inclines me to the belief that life isn't exclusive to Earth—although I don't think we'll find intelligent, able-to-communicate-with-us life; the universe is too big. But at least it's a question that we might be able to answer in the affirmative.