The hardest theme in science fiction is that of the alien. The simplest solution of all is in fact quite profound—that the real difficulty lies not in understanding what is alien, but in understanding what is self. We are all aliens to each other, all different and divided. We are even aliens to ourselves at different stages of our lives. Do any of us remember precisely what it was like to be a baby?

"Introduction to 'Plague of Conscience'", The Collected Stories of Greg Bear (2002)