Meaning of petitio principii

pe•ti•ti•o prin•ci•pi•i

Pronunciation: (pi-tish'ē-ō" prin-sip'ē-ī" Lat. pe-tē'ti-ō" pring-kip'i-ē"), [key]
— Logic. Logic.
  1. a fallacy in reasoning resulting from the assumption of that which in the beginning was set forth to be proved; begging the question.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.