Gangeśa's book Tattvacintāmani ("Thought-Jewel of Reality") was written partly in response to Śrīharśa's Khandanakhandakhādya, a defence of Advaita Vedānta, which had offered a set of thorough criticisms of Nyāya theories of thought and language. In his book, Gangeśa both addressed some of those criticisms and – more importantly – critically examined the Nyāya darśana himself. He held that, while Śrīharśa had failed successfully to challenge the Nyāya realist ontology, his and Gangeśa's own criticisms brought out a need to improve and refine the logical and linguistic tools of Nyāya thought, to make them more rigorous and precise.

Tattvacintāmani dealt with all the important aspects of Indian philosophy, logic, set theory, and especially epistemology, which Gangeśa examined rigorously, developing and improving the Nyāya scheme, and offering examples. The results, especially his analysis of cognition, were taken up and used by other darśanas.

Navya-Nyāya developed a sophisticated language and conceptual scheme that allowed it to raise, analyse, and solve problems in logic and epistemology. It systematised all the Nyāya concepts into four main categories (sense-)perception (pratyakşa), inference (anumāna), comparison or similarity (upamāna), and testimony (sound or word; śabda).

See also

• Nyaya

Sources and reading

• Bimal Krishna Matilal, The Navya-Nyaya Doctrine of Negation: The Semantics and Ontology of Negative Statements in Navya-Nyaya Philosophy (Harvard University Press, 1968) ISBN 0-674-60650-7
• J.N. Mohanty, Classical Indian Philosophy (Rowman & Littlefield, 2000) ISBN 0-8476-8933-6
• Sarvepalli Radhakrishnan, et al. [edd], History of Philosophy Eastern and Western: Volume One (George Allen & Unwin, 1952)