Appeal to Authority

An appeal to authority takes "someone important said it" as if that settled the matter. "A famous physicist endorses this diet, so it must work" — but expertise in physics says nothing about nutrition, and even a real expert can be wrong.^[1] The fallacy isn't citing experts — deferring to genuine, relevant, consensus expertise is reasonable and often necessary. It's treating authority as a substitute for evidence, especially when the authority is outside their field, financially interested, or a lone voice against the consensus. Good reasoning asks what the evidence is, not just who's vouching for it.