ipse dixit
AN ASSERTION WITHOUT PROOF
Ipse-dixitism; Unsupported assertion; Bare assertion fallacy; Ipsedixitism; Αὐτὸς ἔφα; Autòs épha; He himself said it
(ip-sah dicks-it) v. Latin for "he himself said it," meaning the only proof we have of the fact is that this person said it.