A standard of reasoning, or criterion of truth. The sources or bases of knowledge may be distinguished as perception, inference, testimony, analogy, implication in a wider sense than inference, and the interesting category of ‘negative perception’, whereby our senses give us a penumbra of knowledge of what is not present in the sensible world, as well as what is. Different schools of Indian thought accept or reject different ones of these methods. All methods are accepted by Mimamsa; only perception, inference, and testimony by Yoga; only perception and inference by Buddhism and Vaisheshika; and only perception by Carvaka.