Wiktionary
petitio principii
n. 1 (context philosophy logic uncountable English) The logical fallacy of begging the question. 2 (context philosophy logic countable English) A particular argument which commits the fallacy of begging the question; a circular argument.
WordNet
petitio principii
n. the logical fallacy of assuming the conclusion in the premises; begging the question [syn: petitio]
Usage examples of "petitio principii".
That seems rather like confessing that he is aware of the size of his petitio principii.