Well, what are the odds of life even arising in the first place? The conditions had to be pretty perfect for life to arise on Earth, and that can't just be a common occurrence for those conditions to line up as they have, can it? What is extraterrestrial life was hostile, and killed itself? What if we are incapable of perceiving them? What if there [i]is[/i] extraterrestrial life, but we are the only lifeforms capable of intelligence? Too many variables, too many unknowns. There's still so much we're just not sure about the inorganic universe itself. Perhaps we're leading ourselves astray with visions of extraterrestrial life that could give us all the answers.