Nyāya — the science of right reasoning

न्याय

Also written: nyaya · indian logic · gautama nyaya sutra · pramana nyaya · navya nyaya

Nyāya is the tradition's toolkit for argument. Its subject is not what is true but how truth is established — and because every other school had to argue, every other school had to use Nyāya's apparatus, including those that rejected its conclusions.

The four pramāṇas

Pramāṇa	Means
Pratyakṣa	Perception — direct contact of sense with object
Anumāna	Inference — from the seen to the unseen by an invariable relation
Upamāna	Comparison — knowing an unfamiliar thing by its likeness to a known one
Śabda	Reliable testimony — the word of a trustworthy person, above all revealed word

The five-membered inference

Nyāya's syllogism has five steps, and unlike the Aristotelian form it insists on an example — a demand that the general rule be shown to hold somewhere in experience.

Pratijñā — the thesis: 'the hill has fire'.
Hetu — the reason: 'because it has smoke'.
Udāharaṇa — the general rule with an example: 'wherever there is smoke there is fire, as in a kitchen'.
Upanaya — the application: 'the hill has smoke of that kind'.
Nigamana — the conclusion: 'therefore the hill has fire'.

Why the example matters

The requirement of a positive example, and often a negative one ('where there is no fire there is no smoke, as in a lake'), is a demand for empirical grounding built into the logic itself. Nyāya also develops an elaborate theory of fallacy — the hetvābhāsas, reasons that only look like reasons — and Navya-Nyāya, from the thirteenth century, developed a technical language of such precision that it approaches a formal notation.

Nyāya — the science of right reasoning

The four pramāṇas

The five-membered inference

Why the example matters

The six Darśanas — the philosophies

Vaiśeṣika — atoms and the categories of being

Sāṅkhya — the enumeration of the principles

Yoga — Patañjali's system

Pūrva Mīmāṁsā — the philosophy of dharma and of language

Vedānta — the enquiry into Brahman