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Nyaya: Indian logic and theory of knowledge
Nyaya Sutras c. 2nd century AD· School or movement· Asian traditions
DebatedScholars disagree about what happened, what it means, or who said it.
A classical Indian school of logic that asked how we know anything and how to argue correctly.
See it on the Philosophy map →The idea
Idea: knowledge comes only through a fixed set of valid means (pramanas): perception, inference, comparison and reliable testimony. The Nyaya Sutras, credited to Gautama (Akshapada), set out a five-step argument: the hill has fire; because it has smoke; wherever there is smoke there is fire, as in a kitchen; the hill has smoke; so it has fire. They also catalog debating tricks and fallacies. Main objection: Buddhist critics like Nagarjuna asked what validates the means of knowledge themselves.
Why it matters
It gave Indian philosophy its shared rules of debate, and its later 'New Logic' (Navya-Nyaya, from Gangesha, c. 1325) became the technical language of Indian scholarship.
Where it comes from
The Nyaya Sutras and Vatsyayana's commentary (c. 5th century AD) survive in Sanskrit; Nagarjuna's Vigrahavyavartani answers Nyaya-style objections, showing the debate was live.
Still debated
The Sutras' author and date are uncertain; they were probably compiled in layers, perhaps between the 2nd century BC and the 2nd century AD.
Connections (2)
▸Nyaya: Indian logic and theory of knowledge listed valid sources for What can we know?Mostly agreed
The connection
Nyaya answered 'what can we know?' with a list of valid sources of knowledge (pramanas): perception, inference, comparison and reliable testimony. Any claim must trace back to one of them. That turned the question into a checklist, much as a lender asks which document supports each number.
When and how
India, in the Nyaya Sutras (roughly 2nd century AD) and Vatsyayana's commentary (c. 5th century).
How sure are we?
The opening sutras list the four pramanas; rival schools accepted, rejected or added to that list, showing it set the terms.
Debates and open questions
Whether comparison and testimony are truly separate sources or reduce to inference was argued by Buddhist and Vaisheshika critics.
▸Nagarjuna and Madhyamaka (the Middle Way) debated Nyaya: Indian logic and theory of knowledgeMostly agreed
The connection
Nagarjuna attacked Nyaya's means of knowledge: if each needs another to validate it, there is an endless regress; if one validates itself, why not all? Nyaya thinkers replied that his own refutations rely on those very means. The exchange sharpened both schools' logic.
When and how
India, 2nd–5th centuries AD: Nagarjuna's Vigrahavyavartani ('Ending Disputes') and Vatsyayana's replies in his Nyaya commentary.
How sure are we?
The Vigrahavyavartani answers objections stated in Nyaya terms, and the Nyaya Sutras and commentary rebut Madhyamaka-style arguments.
Debates and open questions
Which came first, the Nyaya Sutras or Nagarjuna, and whether his opponents were Nyaya proper, is uncertain.