scientific opinion has generally followed public opinion in the belief that unidentified flying objects either do not exist (the "natural phenomena hypothesis") or, if they do, must represent evidence of a visitation by some advanced race of space travellers (the extraterrestrial hypothesis or "eth"). it is the view of the author that research on ufos need not be restricted to these two alternatives. on the contrary, the accumulated data base exhibits several patterns tending to indicate that ufos are real, represent a previously unrecognized phenomenon, and that the facts do not support the common concept of "space visitors." five specific arguments articulated here contradict the eth: