[1][2] One of the core concepts in Indian epistemology, pramanas are one or more reliable and valid means by which human beings gain accurate, true knowledge.
Three of these are almost universally accepted: perception (pratyakṣa), inference (anumāna), and "word" (śabda), meaning the testimony of past or present reliable experts.
The other three pramanas are more contentious: comparison and analogy (upamāna); postulation or derivation from circumstances (arthāpatti); and non-perception, or proof from absence (anupalabdhi).
[17] Pramāṇa is also related to the Indian concept of yukti (Sanskrit: युक्ति) which means active application of epistemology or what one already knows, innovation, clever expedients or connections, methodological or reasoning trick, joining together, application of contrivance, means, method, novelty or device to more efficiently achieve a purpose.
[20][21] The texts on pramana, particularly by Samkhya, Yoga, Mimamsa and Advaita Vedanta schools of Hinduism, often include in their scope what might be termed "theories of errors"; that is, philosophies regarding the reason for human error, how one may know if one is wrong, and—if so—how one can discover whether one's epistemic method or conclusion was flawed, as well what one ought then do in order to correct it.
[22][23][24] Traditional Hinduism identifies six pramanas as correct means of accurate knowledge and to truths: Pratyakṣa (evidence/ perception), Anumāna (inference), Upamāna (comparison and analogy), Arthāpatti (postulation, derivation from circumstances), Anupalabdhi (non-perception, negative/cognitive proof) and Śabda (word, testimony of past or present reliable experts).
The method of inference is explained by Indian texts as consisting of three parts: pratijna (hypothesis), hetu (a reason), and drshtanta (examples).
For example, they demand Vyapti—the requirement that the hetu (reason) must necessarily and separately account for the inference in "all" cases, in both sapaksha and vipaksha.
[40] Upamana, states Lochtefeld,[41] may be explained with the example of a traveller who has never visited lands or islands with endemic population of wildlife.
Such use of analogy and comparison is, state the Indian epistemologists, a valid means of conditional knowledge, as it helps the traveller identify the new animal later.
The 7th-century text Bhaṭṭikāvya in verses 10.28 through 10.63 discusses many types of comparisons and analogies, identifying when this epistemic method is more useful and reliable, and when it is not.
[44] However, in cases such as deriving the time of a future sunrise or sunset, this method was asserted by the proponents to be reliable.
This form of postulation and deriving from circumstances is, claim the Indian scholars, a means to discovery, proper insight and knowledge.
The schools that do not accept this method, state that postulation, extrapolation and circumstantial implication is either derivable from other pramanas or flawed means to correct knowledge, instead one must rely on direct perception or proper inference.
[49] Specific examples of padartha, states Bartley, include dravya (substance), guna (quality), karma (activity/motion), samanya/jati (universal/class property), samavaya (inherence) and vishesha (individuality).
[49] An absence, state the ancient scholars, is also "existent, knowable and nameable", giving the example of negative numbers, silence as a form of testimony, asatkaryavada theory of causation, and analysis of deficit as real and valuable.
[49][50] Śabda (शब्द) means relying on word, testimony of past or present reliable experts,[4][11] specifically the shruti, Vedas.
[52] He must rely on others, his parent, family, friends, teachers, ancestors and kindred members of society to rapidly acquire and share knowledge and thereby enrich each other's lives.
The mode of Pramana itself in sutra I.6 is distinguished among 5 classes of vritti/mental modification, the others including indiscrimination, verbal delusion, sleep, and memory.
[3] The Nyāya school accepts four[10] means of obtaining knowledge (pramāṇa), viz., Perception, Inference, Comparison and Word.
[55] In Mimamsa school of Hinduism linked to Prabhakara considered the following pramanas as proper:[10] In Advaita Vedānta, and Mimamsa school linked to Kumārila Bhaṭṭa, the following pramanas are accepted:[10][56] Nearly all Vedantins, except Neo-Vedantins for example, accept śabda pramāṇa as a more important pramāṇa than anumāna.
Dignāga's Pramāṇa-samuccaya played a crucial role in shaping the discipline of epistemology (pramāṇaśāstra), blending it with logical discourse.
[62] These two rejected the complex Abhidharma-based description of how in the Vaibhāṣika school and the Sautrāntika Following Scripture approach connected an external world with mental objects, and instead posited that the mental domain never connects directly with the external world but instead only perceives an aspect based upon the sense organs and the sense consciousnesses.
[61] The exact role of logic in Tibetan Buddhist practice and study may still be a topic of debate,[63] but it is definitely established in the tradition.
Ju Mipham remarked in his 19th-century commentary on Śāntarakṣita's Madhyamakālaṅkāra: The Buddha's doctrine, from the exposition of the two truths onward, unerroneously sets forth the mode of being of things as they are.
On the other hand, to claim that analytical investigation in general and the inner science of pramana, or logic, in particular are unnecessary is a terrible and evil spell, the aim of which is to prevent the perfect assimilation, through valid reasoning, of the Buddha's words[66]