Preface
The idea that aliens are in hiding among us—watching, observing, maybe drawing up nefarious plans against us, plotting in secret to conquer us, manipulating society in subtle ways, perhaps even secretly ruling us already, directing world events to further their own ends, alien eyes gleaming from behind their human masks—is one that probably goes way back into history, and probably even into prehistory—back to a time when people from outside your immediate tribal group were regarded with automatic suspicion, and not considered to be really human, not like the People, not like you and me. Even the Romans, at the height of an Empire that anticipated most of the tropes of sophisticated urban society thousands of years before we reinvented them, had this same attitude toward outsiders, toward "barbarians" (so named because they didn't really speak in a human tongue, just made inarticulate animal noises that sounded to the Romans like "bar-bar-bar")—they weren't really human at all.
This attitude is convenient in some ways because, since outsiders aren't human, it allows you to treat them with a total lack of compassion or moral or ethical scruples, and you can slaughter them or rape them or buy them and sell them as you like and still consider yourself to be a good upright honest citizen, operating completely within the Law (since the laws that are designed to keep you from doing these things to other humans don't apply to Them, the non-human Outsiders), a mindset common ever since in everybody from players in the African slave-trade to Hitler and the Nazis.
It's an attitude that has traditionally lead to paranoia, though. Some of the outsiders are easy enough to spot, being obliging enough to have different-colored skin, for instance—but some of the outsiders look just like us. Why, if they dress in human clothes and learn to speak in the human tongue, you might not be able to tell that they were an outsider at all! There might be one living right next door to you, and you wouldn't even know it! You wouldn't even know it—until it was too late! For certainly these outsiders are hiding among us for no good purpose—certainly they must be plotting against us, planning our overthrow, sabotaging the public works, poisoning the wells, setting fire to the cities, stealing our women and children, introducing fluoride into the water supply to pollute our precious bodily fluids . . .
Throughout history, the identity of these Outsiders in hiding among us has changed; at one time or another in European history, they were Christians, pagans, witches, Jews, heretics, Communists.
Today, they are aliens.
The idea that aliens, creatures from outer space, are in hiding among us is very wide-spread today, almost ubiquitous, certainly as widely accepted as many more formally organized faiths, and can be seen in everything from the supermarket tabloids to television documentaries about Roswell to The X-Files.
Print science fiction is where this idea got its start, though, decades before The X-Files was even a gleam in some producer's eye, and is still where the theme is handled with the most imagination and ingenuity (including stuff far weirder and more bizarre than anything you'll see on television), and where it's explored in the most variety and depth (because not all of those aliens are in hiding among us for sinister reasons, you know, nor are all of them interested in administering anal probes or mutilating cattle <does it ever strike you that it must be really dull in outer space, if this is all you can think of to do on a slow weekend?>), with the most sophistication and profundity and power.
And the most entertainment value as well—because, of course, the colorful, fast-paced, and wildly imaginative stories that follow were written to entertain, not to warn humankind of some sinister alien menace . . . although many of them will scare the pants off you nevertheless.
So sit back, relax, make sure the lights are on and the doors are locked, and enjoy. And when your spouse gets home, examine them with a suspicious eye. Are you sure you know where they come from. . . ?