Untruism

No one but a preaching clergyman can revel in platitudes, truisms, and untruisms, and yet receive, as his undisputed privilege, the same respectful demeanour as though words of impassioned eloquence, or persuasive logic, fell from his lips.

Parmenides' philosophy rests, if I am right, on an untruism; it is some slight consolation that his was by no means the last system to be built on such a sandy foundation.

This fickle oscillation is often precipitated by the chameleon-like quality of 'untruisms': 'An untruism is an ambiguous sentence

Aristotle's implicit totalitarianism rests ultimately on a questionable inference from a metaphysical untruism.