It is not only a text on pure logic, but a detailed discussion of anumāna-pramāṇa 比量, the criteria for constructing and refuting inferential proofs (能立 sādhana). Consisting of 29 verses with commentary (vṛtti), it provides detailed definitions, analyses, and examples of the various components of a proof and their relations, including: the thesis (pakṣa 宗), erroneous or pseudo-thesis (似宗 pakṣâbhāsa), a critique of the Nyāya theory of pratijñāvidorodha 宗因相違 (cf. Nyāya Sūtra 5, 2.4), the pakṣadharma 宗法 (established property or properties of a pakṣa which must be properly distributed across the proof for the proof to be valid), asiddha 不成 (claims considered non-established by one or both disputants, use of which renders a proof invalid), examples (喩 dṛṣṭânta) consisting of positive examples (同品 sapakṣa) and negative examples (異品 vipakṣa), the nine types of relations of the positive and negative examples to the rest of the proof 九句因, pseudo-examples (似喩 dṛṣṭāntābhāsa), perception (現量 pratyakṣa-pramāṇa), and pseudo- perception (似現量 pratyakṣābhāsa). The second part, on refutation 能破, takes up the sub-topics of pseudo-refutation (似能破 dūṣaṇâbhāsa) and loss of the debate. It is in this text that Dignāga introduces the three-part (trayo 'vayavā三支作法) inferential proof (sadhāna, 能立) that replaced the five part syllogism (pañcāvayava 五支作法) developed by the non-Buddhist Nyāya school that had also been used by Buddhists up to that point.

The Nyāyamukha caused a stir when first introduced to China. In 647 Xuanzang translated the Nyāyapraveśa 因明入正理論, a primer on Dignāgaʼs logic by Śaṃkarasvāmin 商羯羅主. When Xuanzang completed the Nyāyamukha a few years later in 650, a court Daoist named Lü Cai 呂才, who had a reputation as a braggart (who claimed to be capable of understanding anything no matter how arcane or abstruse), was challenged by a childhood friend, who was now a well-respected Buddhist monk, to see if he could decipher the Nyāyamukha, which had quickly gained the reputation of being the most difficult and obscure text available in Chinese. Lü Cai applied himself and composed a commentary, drawing on three commentaries that had been written by Xuanzangʼs translation assistants on the basis of his expositions while translating. The three commentaries were incommensurate on numerous points, and Lü Cai criticized them in his commentary, touting his own interpretation instead. Taking the opposition of affirming 能立 and denying 能破 as his starting point, he proceeded to interpret the logic through a cosmological yin-yang 陰陽 progression of binary oppositions. His haughty and dismissive airs—albeit couched in polite, purple prose—coupled with his misunderstanding of the purpose as well as the details of Dignāgaʼs system, sparked a major confrontational crisis between Buddhists and Daoists in Xi'an 西安, the capital, which grew more intense until the Emperor finally prevailed on a reticent Xuanzang to declare whether Lü Caiʼs commentary had any merit. Lü Cai lost face and the furor quieted down, but this incident may be the reason why Xuanzang never again translated a hetu-vidyā text (though it doesn't explain why no other major logic texts were translated by subsequent translators, especially given the ever increasing importance hetu-vidyā and pramāṇa-vāda continued to gain in India and eventually Tibet). The story of Lü Cai and the Nyāyamukha, along with the preface to his commentary (which is all that has survived), letters of protest written by prominent Buddhists, and additional details occupy the seventh fascicle of Hui Liʼs 慧立Biography of the Tripiṭaka-master [Xuanzang] of Daci'en Monastery During the Great Tang 大唐大慈恩寺三藏法師傳, T 2053.50.262b.

[Chinese Buddhist Canonical Attributions Database]

[European Language Translations]