Petitio Principii (A). A begging of the question, or assuming in the premises the question you undertake
to prove. Thus, if a person undertook to prove the infallibility of the pope, and were to take for his
premises- (1) Jesus Christ promised to keep the apostles and their successors in all the truth; (2) the popes
are the regular successors of the apostles, and therefore the popes are infallible- it would be a vicious
syllogism from a petitio principii.