Dignaga and Dharmakirti on Perception and Inference

Dignaga (c. 480–540 CE), traditionally counted as a direct or indirect intellectual heir of Vasubandhu's Yogacara circle, is regarded by both traditional doxography and modern scholarship as the founder of the mature Buddhist logico-epistemological school. His central and most influential work, the Pramanasamuccaya ("Compendium of Valid Cognition"), composed in Sanskrit verse with his own prose autocommentary, reduced the accepted instruments of knowledge to exactly two, perception and inference, arguing against the Nyaya school's inclusion of verbal testimony (sabda) and analogy (upamana) as genuinely independent pramanas by treating them as ultimately reducible to inference. Dignaga also devised the influential Hetucakra, the "Wheel of Reasons," a systematic ninefold classification scheme setting out which logical relations between a reason (hetu) and its target property could validly ground an inference and which could not, a tool that later Naiyayika logicians themselves adopted and adapted despite its Buddhist origin.