Petitio Principii

Petitio principii, begging the question, which is the taking of a thing in itself in dispute or not proved or false, for true or for granted, and drawing conclusions from it as such, when it is really dubious, perhaps false, or at least wants to be proved, before any rational inference can be drawn from it. For a discussion of the further question 'Is the syllogism a petitio principii?' see 1 Mill's Log., bk. 2, chap. 3, s. 1.