Meanings
- uncountablehuman sciencesThe logical fallacy of begging the question (i.e., "assuming the conclusion").
- countablehuman sciencesA particular argument which commits the fallacy of begging the question; a circular argument.
A somewhat similar objection has been made by Locke and others, to the effect that the ordinary demonstrative syllogism is a petitio principii.
1869, C. S. Pierce, “Grounds of Validity of the laws of Logic: Further Consequences of Four Incapacities.”, in Journal of Speculative Philosophy1 more example
The Streitberg-Michels Theory is evidently a petitio principii. To explain ē in gēbum, it is from the outset taken for granted, for inadequate reasons of method, that the form must be a perfect. [italics original]
1938, E. Prokosch, A Comparative Germanic Grammar
Synonyms & antonyms
nounthe logical fallacy of assuming the conclusion in the premises; begging the question
Synonym sets from Open English WordNet, CC BY 4.0.
Origin
- Ancient Greekτὸ ἐν ἀρχῇ αἰτεῖσθαι“to assume from the beginning”
- Latinpetītiō prīncipiī
- Englishpetitio principii
From Latin petītiō prīncipiī (literally “an assumption from the beginning”), calque of Ancient Greek τὸ ἐν ἀρχῇ αἰτεῖσθαι (tò en arkhēî aiteîsthai, “to assume from the beginning”).
More words from Latin, Ancient Greek
Full word history & related roots →Cite this entry
petitio principii. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/petitio%20principii
“petitio principii.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/petitio%20principii. Accessed November 5, 2026.
WatkinsX Dictionary, s.v. “petitio principii,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/petitio%20principii.
Source: petitio principii on Wiktionary, CC BY-SA 4.0.