skeptic

The term skeptic refers to a person who questions the veracity or reliability of claims that lack adequate evidence. In ordinary usage, a skeptic applies doubt and demands justification before accepting beliefs or extraordinary propositions. The word comes from the Greek skeptikos, meaning "to look carefully," related to skopos "watching" or "aim."

Philosophical skepticism is a tradition dating to ancient Greece, with Pyrrho and the Pyrrhonists, and later academic skepticism. It questions whether certain knowledge is possible and what methods can justify beliefs. Some forms suspend judgment on all but the most secure propositions; others argue only that knowledge requires strong evidence.

Scientific skepticism, sometimes called skepticism or the skepticism movement, is a modern movement that applies critical thinking and empirical scrutiny to extraordinary claims. Skeptics advocate evidence, testable hypotheses, replication, and falsifiability, and encourage critical examination of sources and logical reasoning. They distinguish between belief and likelihood and emphasize the burden of proof on the claimant.

Practice includes evaluating experimental design, statistics, potential biases, and alternative explanations. Common tools are examining sources, avoiding logical fallacies, using Bayesian reasoning, and demanding reproducible results. Skepticism is not cynicism or denial; it aims to reduce error and uncertainty through disciplined inquiry.

Notable figures associated with scientific skepticism include Carl Sagan and James Randi, and organizations such as the Committee for Skeptical Inquiry and the Center for Inquiry. The term is also applied to a broader approach that promotes critical thinking in science, medicine, and public policy.