विपर्ययः — Proof by the Reverse: Contraposition and the Control

Viparyaya, "reversal", is the device by which a text establishes one thing by stating its opposite. Kauṭilya defines it as "establishing by the reverse" and gives the shortest example in all the tantrayukti lists: after setting out the signs by which a courtier can tell that the king is pleased with him, he adds only "the reverse for one who is not pleased." Suśruta defines it as "the reverse of whatever is stated here": when it is said that "the emaciated, the weak and the timid are hard to treat", the reverse is understood — the sturdy and the rest are easy to treat. Cakrapāṇi defines it as "an example in the contrary direction from what has been set aside", and cites a refrain from Caraka's chapter on gulma: "the things stated as its causes do not suit it, and their opposites do." This last example connects the device with upaśaya, the therapeutic test by opposites that Caraka counts among the five means of knowing a disease. This article shows that viparyaya rests on a polarity in the subject matter — pleased and displeased, weak and sturdy, cause and remedy — and answers three objections: that it is the same as arthāpatti, that reversal is a logical fallacy, and that the word means "error" in the philosophical schools. It concludes that viparyaya is the economy of opposites in a śāstra and the ancestor of the control group: knowing a thing by what happens with its contrary. Series: तन्त्रयुक्तिविमर्शः · Tantrayukti Studies, TY-2026/17. Loci: AŚ 15.1.36–37; Su. Utt. 65.21. Online version: https://sanskritmanthan.in/a/ty-17-viparyaya