hetvabhasa

Hetvabhasa, from Sanskrit hetu meaning “reason” and abhasa meaning “appearance,” is a technical term in Indian logic describing an apparent but defective justification for a conclusion in an inference (anumāna). It denotes a defect in which the stated reason seems to guarantee the conclusion, but the link between the hetu and the sadhya is not genuine or invariable.

In the Nyaya–Vaiśeṣika framework, a sound inference rests on a hetu that exhibits vyapti (invariable concomitance) with the sadhya across all instances. Hetvabhasa occurs when that condition fails or when the reason is misapplied or overextended, so the argument resembles a valid inference on the surface but collapses under scrutiny. The phenomenon highlights how an argument can appear valid due to superficial features, while the underlying logical necessity is absent.

Scholars distinguish between genuinely vyapti-supported reasons and those that merely appear so. Poor use of generalization, faulty illustrative examples, or linguistic presentation that masks a lack of logical necessity can all generate hetvabhasa. The concept has been discussed in classical Nyaya literature and later commentaries, where logicians analyze how a seemingly good argument can mislead and what further analysis is required to repair it.

Historically, hetvabhasa is a recurrent topic in Indian logic, especially in debates among Nyaya and Buddhist logicians. It is used to illustrate the potential for inferential reasoning to go astray and to stress the importance of careful examination of the relationships among hetu, vyapti, and sadhya. See also: Anumāna, Vyapti, Nyaya.