Dignāga

Dignāga (c. 480–540 CE) was a South Indian Buddhist philosopher who founded the pramāṇa tradition of Buddhist epistemology and logic, and transformed the theory of knowledge and argument across all Indian schools. Born near Kāñcī (Kanchipuram), he studied under Vasubandhu or his school, and wrote from a broadly Yogācāra standpoint. His masterpiece is the Pramāṇasamuccaya (“Compendium of the Means of Knowledge”); other works include the Nyāyamukha (“Introduction to Logic”), the Hetucakra (“Wheel of Reasons”) and the Ālambanaparīkṣā (“Examination of the Object”).

Thought

Two means of knowledge

Against the Nyāya philosophers, who accepted four means of knowledge, Dignāga argued that there are only two, corresponding to two kinds of object. Perception (pratyakṣa) grasps the particular (svalakṣaṇa) — the unique, momentary, causally efficient real thing, as it is in itself. Inference (anumāna) grasps the universal (sāmānyalakṣaṇa) — a general feature, which is a mental construction, not a real thing. Testimony and comparison are forms of inference.

Perception free of concepts

Dignāga defined perception as “free of conceptual construction” (kalpanāpoḍha). The moment we name something, classify it, or connect it with a universal — “this is a cow”, “this is blue” — we have left pure perception and entered conceptual thought, which is already a kind of inference. This radical view, that perception is pre-conceptual and concepts never grasp reality as it is, was fiercely opposed by the Naiyāyikas and Mīmāṃsakas, who held that we perceive universals and qualities directly.

Apoha

How then do words and concepts have meaning, if there are no real universals for them to name? Dignāga’s answer was the theory of apoha, “exclusion”: the word “cow” means “not non-cow” — it picks out a class of particulars by excluding everything else. Meaning is negative and differential. The theory was developed by Dharmakīrti and debated for centuries; modern scholars compare it with Saussure’s linguistics (“in language there are only differences”) and with nominalism.

The logic of reasons

Dignāga reformed the theory of inference. He reduced the Nyāya five-membered argument to three members, and stated the three conditions (trairūpya) of a valid reason: it must be present in the subject (smoke on the hill); present in at least some similar cases (smoke in a kitchen with fire); and absent from all dissimilar cases (no smoke in a lake without fire). His Hetucakra (“Wheel of Reasons”) classified all possible reasons in a 3×3 table according to their presence, absence or partial presence in similar and dissimilar cases, showing that only two of the nine are valid — a remarkably formal approach. He also distinguished inference for oneself (svārthānumāna) from inference for others (parārthānumāna), the public argument.

Influence

Dignāga’s work provoked responses from every school: the Naiyāyika Uddyotakara wrote his Nyāya Vārttika largely to refute him; the Mīmāṃsaka Kumārila attacked his theory of apoha. His successor Dharmakīrti systematised and developed his ideas. Through Chinese and Tibetan translation, his logic shaped Buddhist scholarship across Asia; the Chinese Yinming (“science of reasons”) tradition descends from him.