petitio principii

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From Latin petitio principii (literally an assumption from the beginning), calque of Ancient Greek τὸ ἐν ἀρχῇ αἰτεῖσθαι (tò en arkhēî aiteîsthai, to assume from the beginning).

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petitio principii

  1. (philosophy, logic, uncountable) The logical fallacy of begging the question.
  2. (philosophy, logic, countable) A particular argument which commits the fallacy of begging the question; a circular argument.
    • 1869, C. S. Pierce, "Grounds of Validity of the laws of Logic: Further Consequences of Four Incapacities." Journal of Speculative Philosophy.
      A somewhat similar objection has been made by Locke and others, to the effect that the ordinary demonstrative syllogism is a petitio principii.