A false idea or belief, especially one that seems reasonable at first; in logic, a mistake in reasoning.
From Old French “fallacie,” from Latin “fallacia” meaning “deceit, trick,” from “fallere” meaning “to deceive.” It originally described intentional trickery, then expanded to cover misleading reasoning in general.
A fallacy isn’t just being wrong—it’s being wrong in a way that feels convincing. The root idea is “being tricked,” which is why learning fallacies is like learning magic tricks for the mind so you can spot them.
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