Petitio Principii

Aristotle identified the fallacy in Prior Analytics (c. 350 BCE) using the Greek phrase τὸ ἐν ἀρχῇ αἰτεῖσθαι. Boethius translated it as petitio principii around 510 CE — literally "petition of the principle" — in his Latin rendering of Aristotle's logical works. An anonymous late 16th-century English translation rendered petitio as "to beg" rather than "to assume," producing the confusing phrase in use today. The fallacy is thus ancient in substance but accidental in its English name.