Proof

Aristotle . . . to prove what is obvious by what is not is the mark of a man who is unable to distinguish what is self-evident from what is not.

Cabell, James Branch “But I can prove it by mathematics, quite irrefutably. I can prove anything you require of me by whatever means you may prefer,” said Jurgen, modestly, “for the simple reason that I am a monstrous clever fellow.”