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Circular Reasoning

Petitio Principii · Begging the Question

A logical fallacy where the conclusion is assumed in the premise — the argument goes in a circle, proving nothing. "It's true because it's true."

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Origin

First identified by Aristotle in his 350 BCE work Metaphysics as τὸ ἐξ ἀρχῆς αἰτεῖν ("an assumption at the outset"), later translated to Latin as petitio principii. Aristotle discussed it further in Sophistical Refutations and Prior Analytics. The Pyrrhonist philosopher Agrippa later included circular reasoning among his Five Tropes.

Updated February 22, 2026