The founder of Buddhist logic, who rebuilt the theory of knowledge around two sources alone: bare perception and inference.
Dignaga gave Indian philosophy a new rigor. In his Compendium of Valid Cognition he argued that there are exactly two ways to know anything — perception, which grasps the bare particular before thought names it, and inference, which works through concepts — and that all the apparatus of valid reasoning follows from this. His theory of exclusion held that a word means its object only by ruling out what it is not: cow means not-non-cow. The school of logic and epistemology he founded, perfected by Dharmakirti after him, became one of the most sophisticated traditions of reasoning in the ancient world.
“There are but two means of knowledge, perception and inference, for the object known is twofold: the particular and the universal.”
Reduced valid knowledge to perception and inference, founding the most rigorous Indian tradition of reasoning.
Dignaga studied under Vasubandhu and turned the Yogacara analysis of mind toward logic and the theory of knowledge.