Dharmakirti

Dharmakirti studied under Isvarasena, himself a student of Dignaga, and took Dignaga's logic of epistemology to its furthest development. His Pramanavarttika — Commentary on Valid Cognition — is the most rigorous work of epistemology in the Indian tradition. He distinguished two and only two sources of valid knowledge: direct perception and valid inference. Everything else — testimony, analogy, sacred text — must be grounded in one of these or set aside. He developed sophisticated arguments for momentariness (all things exist only for an instant), for the reality of other minds, and for the compatibility of Buddhist philosophy with formal logic. His work influenced every later Tibetan philosophical tradition and, through translations, shaped Islamic and even later European discussions of inference. Yet he was controversial: his account of how the Buddha's teaching could count as authoritative knowledge was seen by some as dangerously naturalistic.