Suggested reading includes The Encyclopedia of Science Fiction's entry on "Aliens", Steve Colgan's Worlds of Possibility blog, Life Everywhere by David Darling, The Science of Aliens by Clifford Pickover and Aliens and Alien Societies by Stanley Schmidt.[first use unknown, but goes back at least to 1940s]General SF term for an extraterrestrial or alien possessing human-level intelligence (see sophont).Etymologically, and in mainstream English the word means "feeling" but is rare and now archaic.[From Poul Anderson's `Polesotechnic League' stories, going back at least to 1963]An evolved biological intelligence.
Yet what if the caterpillar were crawling over the trunk of a tree?Still less common than that term, but has been used by multiple writers..Nor is it used for Earth Humans who must register with the immigration service.In written SF, the KNOWN GALAXY seems increasingly to be inhabited only by Earth Humans.However, Aliens with Forehead Ridges continue to thrive in Hollywood Scifi. In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter.