Skepticism is the discipline of withholding belief when the evidence doesn't earn it. Ancient skeptics — Pyrrho, Sextus Empiricus — went further: they suspended belief on almost everything, hoping the suspension itself would lead to tranquility. Their target wasn't truth but the anxious certainty of dogmatists who claimed to have it.
Modern skepticism narrowed. Descartes used radical doubt as a method: doubt everything that could be doubted, then see what's left. He concluded *cogito ergo sum* — at minimum, the doubter must exist. Hume pushed harder: even basic inferences (the sun will rise tomorrow because it always has) rest on a habit, not a proof. We act as if induction works because we couldn't function otherwise.
The serious version of skepticism today is calibration, not paralysis. Believe in proportion to evidence. Hold strong opinions weakly. Be ready to revise. The cost of failing at this is everywhere — in conspiracy theories, in political tribalism, in the confident asserting of things the asserter hasn't actually checked. The skeptic's discipline is not "doubt everything" but "doubt yourself first."