Nyaya

one of the six orthodox (in the sense of recognizing the authority of the Vedas) systems in Indian philosophy.

A distinction is made between the “old” Nyaya and the “new” Nyaya. The principal text for the old Nyaya was the Nyayasutras of Gautama Buddha (second century B.C. or A.D.). The most important commentaries on it included the Nyayabhasya of Vatsyayana (fourth to fifth centuries), the Nyayavarttika of Uddyotakara (seventh century), and the Nyayavarttikatatparyatika of Vacaspati Misra (ninth century). Other important commentaries on the Nyayabhasya were the Nyayamanjari of Jayanta Bhatta (tenth century) and the Kiranavali of Udayana (tenth century). The principal text for the new Nyaya (Navyanyaya) was the Tattvacintamani of Gangesa Upadhyaya (12th century), supplemented by the numerous works of his followers in the 14th through 18th centuries, including Vasudeva Sarvabhauma, Raghunatha Shiromani, and Mathuranatha.

The old Nyaya dealt with the problems of logic, semantics, grammar, and the theory of knowledge that developed in the definition of the rules for conducting philosophical disputes and in the quest for the criteria for reliable knowledge based on experience. These problems were categorized under 16 basic themes: (1) the sources of true knowledge (sensory perception, logical inference, analogy, and the verbal testimony of authority); (2) the objects of knowledge (including material objects, moral and ethical values, psychological states, and religious phenomena); (3) situations of doubt regarding the authenticity of knowledge; (4) grounds for performing actions; (5) examples that made it possible for the participants in a dispute to reach agreement; (6) bases for proofs; (7) the structure of logical inference; (8) hypothetical conclusions; (9) methods of obtaining new knowledge; (10) disputes leading to the establishment of truth; (11) sophistic arguments; (12) the rules for refuting an opponent; (13) errors in logical inference; (14) signs of a substitution of terms; (15) subterfuges in argumentation; and (16) conditions for recognizing defeat in an argument.

As Nyaya developed, increasing attention was paid to problems of formal logic. Problems of the theory of knowledge, methodology, and debate receded into the background. A classical five-part form of logical inference, which differed radically from the Aristotelian syllogistic, was developed. The terms of the inference were defined according to the rules of the logic of relations rather than the logic of subjects and predicates, and examples played an important part in the structure of the inference. The adherents of Nyaya, who advocated extreme logical realism, did not allow for the possibility of operating with relations having undemonstrable terms; therefore, the five-part structure of the inference retained the features of a conclusion based on analogy or of comparison with a model and could not be reduced to a three-part syllogism.

The intensification of realistic tendencies in the Nyaya theory of knowledge paralleled its rapprochement, and subsequent virtual merging, with the atomistic philosophy of the Vaisheshika, from which Nyaya borrowed all its physics and its system of ontological categories, which it converted into epistemological categories. For Nyaya, “knowledge” acquired the same position as objects in the physical world, and the methods for obtaining and verifying knowledge were of a strictly operationalist character. This transformation was completed in the new Nyaya, whose founders were concerned almost exclusively with the problems of formal logic and logical semantics. They created a complete system of intensional logic, all of whose rules were strictly formalized. In obtaining the terms of a logical inference, the most important operations were those of multistepped negation permitting logical action without quantifiers or a material limitation of properties; this made it possible to wholly exclude instances of the undemonstrability of terms.