Dignāga (bornc. 480ce—diedc. 540) was a Buddhist logician and author of thePramāṇasamuccaya (“Compendium of the Means of True Knowledge”), a work that laid the foundations of Buddhistlogic. Dignāga gave a new definition of “perception”: knowledge that is free from allconceptual constructions, including name and class concepts. In effect he regarded only pure sensation asperception. In his theory ofinference he distinguished between inference for oneself and inference for the other and laid down threecriteria of a valid middle term (hetu)—i.e., that it should “cover” the minorpremise (pakṣa), be present in the similar instances (sapakṣa), and be absent in dissimilar instances (vipakṣa). In hisHetucakra (“The Wheel of ‘Reason’”), Dignāga set up a matrix of nine types of middle terms, of which two yield valid conclusions, two contradictory, and the rest uncertain conclusions. Dignāga’s tradition was further developed in the 7th century byDharmakīrti.