Source Count: 11 | Weighted Score: 17 | Source Confidence: [2/5] | Primary Tier: 1 | Last Updated: June 15, 2025
Keywords: Nagarjuna, catuskoti, tetralemma, Madhyamaka, sunyata, emptiness, Dignaga, Dharmakirti, pramana, Buddhist epistemology, two truths, prasanga, logic
Category Tags: buddhist-philosophy, logic-epistemology, indian-philosophy, eastern-thought
Cross-References: P_4_06 — Buddhist Philosophy & Dependent Origination · P_4_11 — Indian Darshanas · P_4_09 — Non-Dualism & Advaita

QUICK SUMMARY

Buddhist logic represents one of the world's most sophisticated philosophical traditions, developing independently from and in some ways surpassing Aristotelian logic in its treatment of negation, paradox, and the limits of propositional reasoning. At its foundation stands Nagarjuna (c. 150–250 CE), the Madhyamaka ("Middle Way") philosopher whose Mūlamadhyamakakārikā ("Fundamental Verses on the Middle Way") deployed the catuṣkoṭi (tetralemma) — a four-cornered logical framework allowing propositions to be (1) true, (2) false, (3) both true and false, or (4) neither true nor false — to systematically deconstruct all metaphysical claims and demonstrate śūnyatā (emptiness). Later Buddhist logicians Dignāga (c. 480–540 CE) and Dharmakīrti (c. 600–660 CE) built a rigorous epistemological system (pramāṇavāda) incorporating formal inference (anumāna), perception theory, and apoha (exclusion) semantics that engaged directly with Hindu Nyāya logic. This tradition profoundly influenced Tibetan, Chinese, Japanese, and eventually Western analytic philosophy, with contemporary logicians like Graham Priest recognizing the catuṣkoṭi as an anticipation of modern paraconsistent logic.

1. VERIFIED CLAIMS (Tier 1 — Peer-Reviewed / Established)

• Nagarjuna (c. 150–250 CE) composed the Mūlamadhyamakakārikā (MMK) — 27 chapters of Sanskrit verse deploying reductio ad absurdum arguments (prasaṅga) to demonstrate that all dharmas (phenomena) lack intrinsic nature (svabhāva); the MMK is preserved in Sanskrit and in Kumārajīva's Chinese translation (409 CE) and multiple Tibetan versions
• KEY FINDING The catuṣkoṭi (Sanskrit: "four corners") or tetralemma structures Buddhist logical analysis into four positions: (1) X is P, (2) X is not-P, (3) X is both P and not-P, (4) X is neither P nor not-P — Nagarjuna systematically negates all four positions in MMK Chapter 1 to demonstrate the emptiness of causation
• Dignāga (c. 480–540 CE) established Buddhist formal logic (hetvvidyā) with his Pramāṇasamuccaya ("Compendium of Valid Cognition"), defining two valid means of knowledge: direct perception (pratyakṣa), which is non-conceptual, and inference (anumāna), which operates through the "triple characteristic" (trairūpya) of valid reasoning
• Dharmakīrti (c. 600–660 CE) expanded Dignāga's system in his Pramāṇavārttika ("Commentary on Valid Cognition"), which became the foundational logic textbook in Tibetan Buddhist monastic education and remains central to Gelug scholastic training
• The apoha ("exclusion") theory of meaning, formulated by Dignāga and refined by Dharmakīrti, holds that words do not refer to positive entities but function by excluding everything the term does not denote — a nominalist semantic theory that parallels aspects of Ferdinand de Saussure's later structural linguistics
• KEY FINDING Nagarjuna's two-truth doctrine (saṃvṛti-satya / paramārtha-satya) distinguishes conventional truth (the practical validity of everyday language and logic) from ultimate truth (the recognition that all conceptual frameworks, including logic itself, are empty of inherent existence) — this is not irrationalism but a meta-logical position about the limits of conceptual thought
• The Tibetan monastic debate tradition (rtsod pa), practiced in major Gelug monasteries since the 15th century, uses formalized logical structures derived from Dharmakīrti, with monks physically gesturing (hand-clapping, foot-stamping) to mark logical moves — this living tradition maintains Buddhist logic as a practiced discipline

2. CREDIBLE CLAIMS (Tier 2 — Academic / Debated but Supported)

• Graham Priest (City University of New York) has argued in In Contradiction (2006) and subsequent publications that the catuṣkoṭi anticipates modern paraconsistent and dialethic logic — systems that allow true contradictions — representing a genuine alternative to classical Aristotelian logic rather than mere confusion
• Jay Garfield (Smith College, later Yale-NUS) has argued that Nagarjuna's arguments are best understood as a form of "therapeutic philosophy" comparable to Wittgenstein's later work — both figures use logical reasoning to demonstrate the limits of logical reasoning without claiming to establish a positive metaphysical position
• The Nyāyabindu of Dharmakīrti contains a theory of momentariness (kṣaṇikavāda) — the claim that all phenomena exist for only a single moment — supported by arguments about causation and temporal identity that Mark Siderits has compared to Humean skepticism about persistent substances
• Buddhist-Nyāya debates in India (5th–12th centuries CE) produced some of the most sustained philosophical arguments in world history, with Hindu logicians like Uddyotakara (6th century) and Vāchaspati Miśra (9th century) writing detailed refutations of Dignāga and Dharmakīrti, who in turn responded to earlier Nyāya critiques
• Chinese Buddhist logic (yinming 因明) entered East Asia through Xuanzang's (602–664 CE) translations of Dignāga and Dharmakīrti after his pilgrimage to Nalanda; the tradition influenced medieval Chinese philosophical discourse but was eventually eclipsed by Chan/Zen methods that rejected formal scholasticism

3. SPECULATIVE CLAIMS (Tier 3 — Possible but Unverified)

• Scholars have suggested that Nagarjuna's tetralemma may have influenced Greek skepticism through Indo-Greek cultural contact — Pyrrho of Elis (c. 360–270 BCE) traveled with Alexander's army to India and his "suspension of judgment" (epochē) on all dogmatic positions bears structural similarity to Madhyamaka, though direct textual transmission remains unproven
• The formal parallels between apoha semantics and modern computational approaches to meaning (distributional semantics, word embeddings defined by contextual contrast) have led some AI researchers to explore Buddhist logic as a framework for handling vagueness and context-dependence in natural language processing
• Nāgārjuna's identity and biography remain partially obscure — Buddhist traditions attribute over a dozen texts to him, but modern scholarship (following David Ruegg and Jan Westerhoff) accepts only about five as definitively authored by the same individual

4. DUBIOUS CLAIMS (Tier 4 — No Credible Source / Contradicted by Evidence)

• DEBUNKED The claim that Buddhist logic "rejects reason" or is "mystical irrationalism" — Dignāga and Dharmakīrti developed one of the most rigorous formal logical systems in the ancient world, complete with rules of valid inference, fallacy classification, and systematic debate protocols
• Claims that the catuṣkoṭi is "logically impossible" under any interpretation — Priest and others have shown it is formally consistent within paraconsistent logical frameworks, and Nagarjuna's usage is better understood as meta-logical rather than violating the law of non-contradiction at the object level

Counter-Arguments & Criticisms

• Brendan Gillon and other analytic philosophers have argued that interpreting the catuṣkoṭi as "paraconsistent logic" may import modern formal concepts that distort the original philosophical context, which operated within different background assumptions about language and reality
• The "therapeutic" reading of Nagarjuna (Garfield, Siderits) has been challenged by scholars like Tom Tillemans who argue that Prāsaṅgika Madhyamaka does have substantive philosophical commitments, not merely diagnostic ones
• The relationship between Dignāga/Dharmakīrti's epistemology and Nagarjuna's Madhyamaka is deeply contested — scholars (especially in the Tibetan Gelug tradition) reconcile them, while others argue they represent incompatible philosophical programs

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BIBLIOGRAPHY

1. Nagarjuna | 1995 | ∅ | The Fundamental Wisdom of the Middle Way: Nāgārjuna's Mūlamadhyamakakārikā | ∅ | ∅ | Translated by Jay Garfield | ∅ | doi:10.1093/oso/9780195103175.001.0001 | ∅ | ∅ | Oxford: Oxford University Press
2. Priest, Graham | 2006 | ∅ | In Contradiction: A Study of the Transconsistent | ∅ | ∅ | Oxford: Oxford University Press | ∅ | isbn:9780199263294 | ∅ | ∅ | ∅. DOI: 10.1093/acprof:oso/9780199263301.003.0015
3. Dignāga | 1968 | ∅ | Dignāga, On Perception | Pramāṇasamuccaya | ∅ | Translated by Masaaki Hattori as Cambridge: Harvard University Press | ∅ | isbn:9780674209305 | ∅ | ∅ | ∅. DOI: 10.1017/s0035869x00129752
4. Dreyfus, Georges | 1997 | ∅ | Recognizing Reality: Dharmakīrti's Philosophy and Its Tibetan Interpretations | ∅ | ∅ | Albany: SUNY Press | ∅ | isbn:9780791430982 | ∅ | ∅ | ∅. DOI: 10.1017/s0034412598254746
5. Siderits, Mark; Shōryū Katsura | 2013 | ∅ | Nāgārjuna's Middle Way: Mūlamadhyamakakārikā | ∅ | ∅ | Somerville: Wisdom Publications | ∅ | isbn:9781614290502 | ∅ | ∅ | ∅
6. Westerhoff, Jan | 2009 | ∅ | Nāgārjuna's Madhyamaka: A Philosophical Introduction | ∅ | ∅ | Oxford: Oxford University Press | ∅ | isbn:9780195384963 | ∅ | ∅ | ∅
7. Tillemans, Tom | 1999 | ∅ | Scripture, Logic, Language: Essays on Dharmakīrti and His Tibetan Successors | ∅ | ∅ | Somerville: Wisdom Publications | ∅ | isbn:9780861711568 | ∅ | ∅ | ∅
8. Garfield, Jay; Graham Priest | 2003 | "Nāgārjuna and the Limits of Thought" | Philosophy East and West | ∅ | 53.1::1–21 | ∅ | ∅ | doi:10.1353/pew.2003.0004 | ∅ | ∅ | ∅
9. Matilal, Bimal Krishna | 1998 | ∅ | The Character of Logic in India | ∅ | ∅ | Albany: SUNY Press | ∅ | isbn:9780791437394 | ∅ | ∅ | ∅
10. Ruegg, David Seyfort | 1981 | ∅ | The Literature of the Madhyamaka School of Philosophy in India | ∅ | ∅ | Wiesbaden: Otto Harrassowitz | ∅ | isbn:9783447022040 | ∅ | ∅ | ∅
11. Stcherbatsky, F | 1930–1932 | ∅ | Buddhist Logic | ∅ | ∅ | Th | ∅ | isbn:9780486204802 | ∅ | ∅ | 2 vols; Leningrad: Academy of Sciences; Reprinted New York: Dover, 1962

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