The corollary argument exists against their existence. Bigelow has posited that "...some 100 million Earthlings have been abducted by aliens."

Why is it that not one of those people has come back with so much as an ashtray or rest room towel? Even a few micro grams from a UFO could be subjected to mass spectroscopy, and the isotopic signature would be proof of extraterrestrial origin. There IS something strange going on here. People are not telling the truth.