Where Do Aliens Come From?

I want to tell you where aliens come from — not which galaxy or dimension, but rather how humans, over the past few centuries, have come to conceive of extraterrestrial life. But before we start, we must briefly note that there are already a few very good reasons to be sceptical of recent reports of encounters with alien beings. This is not at all to say that such beings do not exist, but only that the presumptions behind reported encounters almost always reveal a strong terrestrial bias: an inability to imagine the real conditions, imposed by the universe itself, on any potential interstellar voyage.