(Sanskrit: “measuring along some other thing,” or “inference”), in Indian philosophy, the second of the five means of knowledge ( pramāṇa) that enable man to have accurate cognitions. inference occupies a central place in the Hindu school of logic ( Nyāya). This school worked out a syllogism that has the form of an argument rather than a formula and that goes through five stages: (1) the proposition (pratijñā, literally “promise”), (2) the ground (hetu), (3) the illustration (udāharaṇa), (4) the application (upanaya), and (5) the conclusion (nigamana). A syllogism is vitiated by a fallacious ground; this is called hetvābhāsa (“the mere appearance of a ground”). A number of types of invalid grounds are distinguished: simple error, contradiction, tautology, lack of proof for the ground, and inopportunity. See also pramāṇa.