(If you want on or off this list please freepmail me.)
Ad ignorantiam fallacy - (argument from ignorance). Asserting the truth of any proposition on the basis that what is asserted has never disproved or what is denied has never been proved; or that there is no evidence for the thing denied, or, against what is asserted.
Debate about the mystic, paranormal, or occult proceed largely by arguing ad ignorantiam. The fallacy also forms the basis for most medical quackery tricked up with a lot of medical jargon.
Examples:
"It has never been proved, nor can it be, that clairvoyance does not exist, therefore, it must exist." "It has never been proved, nor can it be, that clairvoyance exists, therefore, it cannot exist."
"Studies show that many people using fibrilopymesium hypochloride recover completely from their diseases. No study has ever failed to show this." There is no proof it doesn't work, therefore it must work. "Studies show that some people using fibrilopymesium hypochloride never recover from their diseases. Every study shows this." There is no proof it does work, therefore, it must not work.
Argument from ignorance is obviously very useful.
Hank
Boy, have I had enough of that lately to last a lifetime!