Paradox
Etymology
From Greek "paradoxon," from "para," "contrary to," plus "doxa," "opinion" or "expectation." So a paradox is literally something running against what everyone takes for granted. The word kept that flavor: not merely false, but startling — a claim that offends common sense and then, sometimes, turns out to be right.
noun · /PAIR-uh-doks/
A statement or situation that seems self-contradictory or absurd yet may express a genuine truth.
What it names
The productive friction of an idea that can’t be true and can’t be dismissed — the signal that your assumptions, not reality, are what need fixing.
Example
The paradox of tolerance holds that a society tolerant without limit will eventually be dismantled by the intolerant it tolerates.
Related idea
A paradox at least gestures at truth beneath the contradiction; a tautology has the opposite problem, being so trivially true that it says nothing at all.