thumb|260px|The means to correct knowledge, according to ancient Nyayasutras
The Nyāya Sūtras is an ancient Indian Sanskrit text composed by , and the foundational text of the Nyaya school of Hindu philosophy. The date when the text was composed, and the biography of its author is unknown, but variously estimated between 6th-century BCE and 2nd-century CE. The text may have been composed by more than one author, over a period of time.
The Nyāya Sūtras is a Hindu text, notable for focusing on knowledge and logic, and making no mention of Vedic rituals. The first book is structured as a general introduction and table of contents of sixteen categories of knowledge.
The Nyaya sutras cover a wide range of topics, including Tarka-Vidyā, the science of debate or Vāda-Vidyā, the science of discussion. The Nyāya Sutras are related to but extend the Vaisheshika| epistemological and metaphysical system. Later commentaries expanded, expounded and discussed Nyaya sutras, the earlier surviving commentaries being by Pakṣilasvāmin Vātsyāyana (5th–6th century CE), followed by the Nyāyavārttika of Uddyotakāra (6th–7th century CE), Vācaspati Miśra's Tātparyatīkā (9th century CE), Udayana's Tātparyapariśuddhi (10th century CE), and Jayanta's Nyāyamañjarī (10th century CE).
Author and chronology
The Nyaya-sutras is attributed to Gautama, who was at least the principal author.
It is likely, states Jeaneane Fowler, that Nyaya and the science of reason stretch back into the Vedic era; it developed in the ancient Indian tradition that involved "dialectical tournaments, in the halls of kings and schools of Vedic philosophers", and Gautama was the one who distilled and systematized this pre-existing knowledge into sutras, or aphoristic compilations called nyayasutras.
The Nyaya school of Hinduism influenced all other schools of Hindu philosophy, as well as Buddhism. Despite their differences, these scholars studied with each other and debated ideas, with Tibetan records suggesting that Buddhist scholars spent years residing with Hindu Nyaya scholars to master the art of reasoning and logic.
Structure
The text is written in sutra genre. A sutra is a Sanskrit word that means "string, thread", and represents a condensed manual of knowledge of a specific field or school. Each sutra is any short rule, like a theorem distilled into few words or syllables, around which "teachings of ritual, philosophy, grammar or any field of knowledge" can be woven. Sutras were compiled to be remembered, used as reference and to help teach and transmit ideas from one generation to the next.
The Nyayasutra is divided into five books, each book subdivided into two chapters each. The structure of the text is, states Potter, a layout of ahnikas or lessons served into daily portions, each portion consisting of a number of sutras or aphorisms.
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| width= 450px style="text-align: left;" | Subject matter and statement of purpose of the text. Four reliable instruments of correct knowledge. Definitions. Nature of argument and nature of the process of valid proof.
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| width= 450px style="text-align: left;" | How to analyze opposing views, presents its theory of five-membered arguments, correct conclusions are those where contradictions do not exist, theory of reasoning methods that are flawed, what is a quibble and how to avoid it.
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| width= 450px style="text-align: left;" | Presents its theory of Doubt. Discusses epistemology, when perception, inference and comparison is unreliable and reliable. Theory that the reliability of testimony depends on the reliability of the source. Theory that the testimony in the Vedas are a source of knowledge and inconsistencies are either defects or choices in the text, the best way to understand the Vedas is to divide it into three: injunction, descriptions and reinculcations.
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| width= 450px style="text-align: left;" | Instruments of knowledge are fourfold, Confusion caused by presumption and prejudice, Sound is noneternal theory, Theory of three meaning of words (vyakti, akrti and jati)
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| width= 450px style="text-align: left;" | presents its theory of body, followed by theory of sensory organs and their role in correct and incorrect knowledge, states that the soul is not a sense organ nor an internal organ.
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| width= 450px style="text-align: left;" | presents its theory of soul (self, atman), that the essence of a person and source of judgments is the soul, states its "judgment is non-eternal" theory, presents theory of Karma
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| width= 450px style="text-align: left;" | Presents its theory of defects, then its theory that "everything has cause, and consequences", and its "some things are eternal, some non-eternal" theory. Defines and describes Fruits, Pain, Release.
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| width= 450px style="text-align: left;" | Presents correct knowledge is necessary and sufficient to destroy defects. Both whole and part must be known. Establishes external world exists, and phenomenon are as real as objects. Refutes the "everything is false" theory. Presents ways to produce and maintain correct knowledge, Need to seek and converse with those with knowledge.
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| width= 450px style="text-align: left;" | 24 futile rejoinders, how to avoid errors and present relevant rejoinders
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| width= 450px style="text-align: left;" | 22 ways of losing an argument
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Content
thumb|The first ten sutras of the text in [[Sanskrit|upright=1.3]]
The first sutra 1.1.1 of the text asserts its scope and the following sixteen categories of knowledge as a means to gain competence in any field of interest:
These sixteen categories cover many sections of the text. The verse 1.1.2 of the Nyāya Sūtra declares the text's goal is to study and describe the attainment of liberation of soul from wrong knowledge, faults and sorrow, through the application of above sixteen categories of perfecting knowledge.
Means of attaining valid knowledge
The Nyaya-sutras assert the premise that "all knowledge is not intrinsically valid", that "most knowledge is not valid unless proven" and "truth exists whether we human beings know it or not". However, states Fowler, the text accepts the foundation that "some knowledge is self evident" and axiomatic in every field of knowledge, which can neither be proven nor needs proof, such as "I am conscious", "I think" and "soul exists". Furthermore, the text presents its thesis that knowledge is not self-revealing, one must make effort to gain knowledge and this is a systematic process that empowers one to learn correct knowledge, and abandon incorrect knowledge.
The Nyāya sutras asserts and then discusses four reliable means of obtaining knowledge (pramāṇa), viz., Perception, Inference, Comparison and Reliable Testimony. Gautama dedicates many sutras to discuss both the object and subject in the process of perception, and when senses may be unreliable. Erratic eyesight or other senses (Avyabhicara) can be a source of doubt or false knowledge, as can prejudgmental or prejudicial state of mind, states the Nyayasutras.
The epistemic rationale for inference as a reliable source of knowledge, and Nyaya's theory has been a major contribution to the diverse schools of Indian Darshanaparampara, and other schools looked up to Nyaya scholars for insights on correct knowledge and incorrect knowledge through inference. The text states one must not confuse coexistence as a universal relation, and that while deduction and induction both are useful and valid means for gaining true knowledge, it lists rules when this method can lead to false knowledge.
Upamana: Comparison and analogy
The word upamana, states Fowler, is a compound of upa (similarity) and mana (knowledge). It is a means of gaining knowledge based on "similarity, comparison, analogy", and considered reliable in Nyaya and many schools of Indian Darshanaparampara (but not in Vaisheshika and Charvaka, or Buddhism).
The Nyayasutras define upamana as the knowledge of a thing based on "its likeness to another thing which is familiar". It differs from Anumana (inference) in lacking a direct or immediate causal relation. It differs from Pratyaksha (perception), states the text, in using a linguistic referent and the foundation of pre-existing knowledge within the individual and what he learnt from his teachers, friends, family and past knowledge inherited from the wise, through a process of social cooperation. The Upamana method is secondary, it relies on perception, combined with linguistic referent and context. Comparison is, in Nyayasutras, the process of permeating or infusing hypothesis, examples and tests, thus leading to objectivity and correct knowledge about something new and what one already presumes to know.
Shabda: Testimony and reliable sources
Śabda (, Word), in Nyayasutras, means relying on word, testimony of a reliable source. Sabda-pramana has been an accepted and reliable method to knowledge by all orthodox schools of Hinduism including Nyaya, asserting that a human being needs to know numerous facts, and with the limited time and energy available, he can learn only a fraction of those facts and truths directly. He must rely on others, his parents, family, friends, teachers, ancestors and kindred members of society to rapidly acquire and share knowledge and thereby enrich each other's lives. This means of gaining correct knowledge is either spoken or written, but it is through Sabda (words).
The reliability of the source is important, and legitimate knowledge can only come from the Sabda of reliable sources. Some schools, such as Charvaka, state that this is never possible, and therefore Sabda in the Vedas or anyone else, can never be a proper pramana. Other schools debate means to establish reliability.
Theory of proper argument
The text, in sutras 1.1.32 and 1.1.39, presents its theory of proper arguments, stating that a proper argument must include five components:
- pratijna – the proposition or hypothesis (that which needs to be proved or decided)
- hetu – the reason (can be positive or negative)
- udaharana – the general rule (that which is independently confirmed or confirmable)
- upanaya – the application of the rule (validity test, or example to the instance)
- nigamana – the conclusion (the hypothesis is either true or false or in doubt)
The text defines and aphoristically discusses each of these.
- There is a fire on the hill
- Because there is smoke on the hill
- Whenever there is smoke, there is a fire
- The hill is smoky
- Therefore, there is a fire on the hill
Theory of doubt as incomplete knowledge
The Nyayasutras define and discuss Samsaya (, doubt) in sutras 1.1.23, 2.1.1 to 2.1.7, 3.2.1, 4.2.4 among others. This discussion is similar to those found in other schools of Hindu philosophy, expands on the theory of doubt presented by Kanada in the Vaisheshika school, but disagrees with the Charvaka school's theory of doubt and consequent "there is no empirical knowledge ever".
Hetvabhasa, theory of errors
The Nyayasutra defines error as knowledge, an opinion or a conclusion about something that is different from what it really is. The Nyaya theory shares ideas on the theory of errors with Advaita Vedanta, Buddhism and Mimamsa schools of Indian philosophies, states Rao, and these schools likely influenced each other.
The text identifies and cautions against five kinds of fallacious reasoning (hetvabhasa) in sutra 1.2.4, discussing each in the sutras that follow, stating that these lead to false knowledge, in contrast to proper reasoning (hetu), which leads to true knowledge. The five forms of bogus reasoning identified by the text, states Ganeri, are:
- the wandering or erratic (Nyayasutra 1.2.5)
- the contradictory (Nyayasutra 1.2.6)
Theory of causality
The Nyayasutras dedicate many sections on causality and causal relations (Karana, ), particularly Book 4. Causes, in Nyaya view states Fowler, are "antecedents of their effects invariably and unconditionally". A specific effect is produced by a specific cause (plurality in causes is accepted). A specific cause produces a specific effect and no other (plurality in effect, or contradictory effect is not accepted). There cannot be reciprocity to a cause; either we misunderstand the cause or misapprehend the effect.
The text identifies three types of causes – inherent or material cause (Samavayi-karana), non-inherent cause (Asamavayi-karana), and efficient cause (Nimitta-karana). These, it states, arise from Dravya (substance), Guna (quality) and Karma (action).
Theory of negatives
The text seeds the theory of negative entities, where both being and non-being, presence and absence of something is considered correct and useful knowledge. Absence of a book on a table or absence of particular color in a painting has a place in its epistemic process, in addition to positively verifiable characteristics of the table or a painting.
In Nyayasutra's Book 4, Chapter 1 examines what causes production and destruction of entities (life, matter) in the universe. It considers many hypotheses, including Ishvara. Verses 19–21 postulate that Ishvara exists and is the cause, states a consequence of the postulate, then presents contrary evidence, and from contradiction concludes that the postulate must be invalid.
Other scholars of Nyaya school reconsidered this question and offered arguments for what is God (Ishvara) and various arguments to prove the existence of Ishvara. The 5th century CE Nyaya school scholar Prastapada, for example, revisited the premise of God. He was followed by Udayana, who in his text Nyayakusumanjali, interpreted "it" in verse 4.1.21 of Nyaya Sutra above, as "human action" and "him" as "Ishvara", then he developed counter arguments to prove the existence of Ishvara, a reasoning that fueled the debate and disagreements on God in Neo-Nyaya and other Hindu traditions of 2nd millennium CE.
Soul, self exists, inner freedom
A large part of the third book of the Nyayasutras is dedicated to the premise and the nature of a Self (soul, atman) and its relation to knowledge, liberation from sorrow and inner freedom (moksha).
Philosophy: a form of Yoga
The sutras 4.2.42 to 4.2.48 of Nyayasutras, states Stephen Phillips, state that "philosophy is a form of yoga".
The text recommends yogic meditation in quiet places such as a forest, cave or sandy beach in sutra 4.2.42, that the knowledge seeker should purify one's soul by Yamas, Niyamas and spiritualism of yoga in sutra 4.2.46. Vatsyayana wrote in his commentary on Nyayasutras, for example, that meditation is that which enables the mind to contact one's soul, which is accompanied by a conscious eagerness to get at the truth, and such meditation is an essential practice to gain true knowledge. In some cases, asserts the text, it is better to avoid arguing with hostile opponents and use methods of knowledge like "a fence is used to safeguard the growth of seeds".
Commentaries
The earliest surviving complete bhasya (review and commentary) on Nyaya Sutras is by Vatsyayana. Another often studied surviving commentary on the text is credited to Vacaspati Mishra from about 9th century CE.
Numerous other commentaries are referenced in other Indian historical texts, but these manuscripts are either lost or yet to be found. Starting around 11th- to 12th century CE, Udayana wrote a primary work, that built upon and expanded the theories on reason found in Nyayasutras. Udayana's work created the foundation for Navya-Nyaya (new Nyaya) school.
Influence
On Hinduism's soul, Buddhism's no-soul debate
The Nyaya-sutras have been one of the foundations for the historic debate between Hinduism's premise that purusa (spirit, ultimate reality) and atman (selfhood, soul) exists, and Buddhism's premise that there is voidness and anatta (no-soul). In Nyaya-sutra, the Buddhist premises and arguments to refute those premise are found in many chapters,
Nagarjuna's Madhyamika-karika targets Nyaya-sutra, among other Hindu texts, for his critique and to establish his doctrine of no self and voidness. In this text, and Vigrahavya-vartani, he presents his proof of voidness by challenging the Pramanas at the foundation of Nyaya-sutras. In his work Pramana-vihetana, Nagarjuna, takes up each of the sixteen categories of knowledge in Gautama's Nyaya-sutras at the foundation of Nyaya's discussion of "soul exists and the nature of soul in liberation process", and critiques them using the argument that these categories are relational and therefore unreal.
The Buddhist thesis that all things are negative in nature (inasmuch as a thing's nature is constituted by its differences from others), or the Hindu thesis counter-arguing the Buddhist thesis, have been accepted, is still unclear because nothingness cannot be proved and existence of soul has been claimed solely on the basis of personal feeling and experience.
On Vedanta traditions
The Nyayasutras were influential to the Vedanta schools of Hindu philosophy, and provided the epistemological foundations. The terms Nyaya and Mimamsa were synonymous, states Hajime Nakamura, in the earliest Dharmasutras of 1st millennium BCE. Over time, Nyaya, Mimamsa and Vedanta became three distinct and related schools.