Pramāṇa [“proof, means of knowledge”] refers to epistemology in Indian philosophies. Ancient and medieval Indian texts identify six pramanas as correct means of accurate knowledge and to truths: perception (pratyakṣa), inference (anumāna), comparison and analogy (upamāna), postulation, derivation from circumstances (arthāpatti), non-perception as negative/cognitive proof (anupalabdhi) and testimony from reliable experts (Śabda).

Each of the Six Schools further categorize these in terms of conditionality, completeness, confidence, and possibility of error. The science and study of Pramanas is called Nyaya.

In order of decreasing pramana count, the various schools are listed below:

Mimamsa and Advaita Vedanta — All six are useful and can be reliable means to knowledge.

Nyāyá — Naiyayikas accepted four valid means (pramaṇa) of obtaining valid knowledge (pramana): perception (pratyakṣa), inference (anumāna), comparison (upamāna) and testimony of reliable sources (śabda).

Sāmkhya, Yoga, Vishishtadvaita Vedanta, and Dvaita Vedanta — Perception, inference, and testimony.

Buddhism — Perception and inference.

Vaiśeṣika — Perception and inference.

Carvaka — Charvakas accept only perception as a reliable source of knowledge, and rejected inference as a means to establish valid, universal knowledge, and metaphysical truths. Consequently, whatever one infers from a set of observations can be doubted, i.e., inferred knowledge is conditional.