Proof by assertion

Proof by assertion is the name given to the Logical fallacy in which a proposition is repeatedly put forth without regards to contradictory evidence. The argument may be stated to be true because of its repetition, or via a variant of the appeal to belief or appeal to authority fallacies.

A quote sums the arguments "proof by assertion" and "appeal to belief" quite nicely; "No amount of belief makes something a fact" -- James Randy.