petitio principii

Meanings

1. The logical fallacy of begging the question (i.e., "assuming the conclusion").
2. A particular argument which commits the fallacy of begging the question; a circular argument.

Etymology

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”).