 There is also an important variant where the truth of “A is B” is not being established, but only the fact that it would follow from an acceptance (abhyupagama) of A being C. Thus a debater can present an opponent with a prasaṅga (consequence) of the sort: “It would follow absurdly that A would be B, because of being C.” Such a consequence will constitute the key step in a proof by reductio ad absurdum, a proof that will culminate in a type of contraposition, turning on modus tollens. When the pervasion in the consequence holds and the opponent understands that A is not in fact B, the opponent will then be led by a “contraposition of the consequence” (prasaṅgaviparyaya, literally “reversing the consequence”) to understand that A is not in fact C because of not being B. Both these structures, i.e., proofs by logical reasons and consequences, are to be found in Indian and Tibetan writing on a variety of subjects.