An ability to elude detection and confirmation, particularly by mainstream thinkers, is a presumed characteristic of the Visitors. Having dropped in on a couple of UFO conventions and visited Roswell, New Mexico, and its UFO museum, I've come to the conclusion that it's not possible to win an argument about space aliens. True believers and skeptics rarely go over to the other side. I think it's fair to say, however, that flying-saucer aliens lack scientific stature. If they insist on being so jumpy, if they insist on abducting people in the middle of the night when no one else can verify their presence, then they have no right to enter a reputable natural history museum.
Most people operate from the same instinct, which is to know the truth about the universe.
As many writers have noted, aliens are, for some people, the secular equivalent of angels and demons and ghostly spirits. What makes them so intriguing is that even scientists will concede that alien beings could very well be out there somewhere. Therefore the scenario in which they come to Earth requires only some imagination about transportation. Humans could theoretically colonize the galaxy in a million years or so, and if they could, astronauts from older civilizations could do the same. This is known as the Fermi paradox.