Ø Nyāya school of Indian Philosophy was founded by Gotama who is also known as Aks̩apāda.
Ø Nyāya is also known as:
1. Pramāns̩astra: science of logic and epistemology.
2. Hetuvidya: Science of causation
3. Vādavidya: Science of debate
4. anvīks̩kī: Science of critical study
5. tarksastra: Science of reasoning
Ø Nyāya-sutra is the main text written by Gotama, on which Vatsayan wrote a commentary which is called Nyāya-bhāsya.
Ø Uddyotakara wrote his Vartika on Nyāya-bhāsya, Vāchaspati wrote commentary on Vartika which is called tatparya-tika.
Ø Nyāya is a school of atomistic pluralism and logical realism. It is allied to vaisesika syatem (samanantara). Vaisesika develops Ontology and Metaphysics, Nyaya develops Logic and epistemology.
Ø Both agree in viewing the earthly life as full of suffering, as bondage of the soul.
Ø According to Nyāya there are two kinds of knowledge: (i) valid (pramā): it is right apprehension of an object, i.e., yatharthānubhāva (presentation of an object as it is). (ii) invalid (apramā).
Ø Nyāya maintains the ‘theory of correspondence’- paratah̩ prāmānya.
Ø There are four means of valid knowledge (presentative cognition) according to Nyāya:
1. Perception- pratakshya
2. Inference- anumana
4. Testimony- sruti
Ø Invalid knowledge includes:
1. Smrti- memory
3. Viparyaya- error (misapprehension)
4. Tarka- hypothetical reasoning
Ø Valid knowledge corresponds to its object (yathartha and avisavadi) and leads to successful activity (pravrttisamarthya).
Ø Invalid knowledge does not correspond to its object (ayathārtha and visamvādi) and leads to disappointment and failure (pravrttisamvada).
Ø Nyaya theory of knowledge is Realistic and Pragmatic.
Ø Perception is ‘non-erronous cognition’ according to Gotama. There are two stages in perception:
1. Nirvikalpa (indeterminate)
2. Savikalpa (determinate)
Ø Perception is ‘unassociated with a name’ (avyapadeshya) which means ‘indeterminate’, and it is ‘well-defined’ (vyayavāsyatmaka) means determinate.
Ø ‘Percepts without concepts are blind and concepts without percepts are empty.’
Ø Perception is of two kinds:
1. Laukika (ordinary): it is perception of the usual type and is of two kinds, i.e., manas (internal) and external (bāhya).
2. Ālaukika (extra-ordinary): it is the perception in an unusual way. It is of three types:
i. Samanyalaksana: perception of universals. Eg. Cowness in cow.
ii. Jnanalaksana: perception through association. The theory of illusion (anyathakhyati) is based on this type of perception.
iii. Yogaja: immediate perception by yogins through meditatios.
Ø Yogaja of Nyaya is like Kevaljnana of Jainism, Bodhi of Buddhist, kaivalya of Sankhya-yoga and aproksanubhuti of Vedantins.
Ø Inference (anumana): It is knowledge (mana0 which arises after (anu). It is mediate and indirect. It arises through a ‘mark’ the middle term (linga or hetu). The middle term is connected invariably with the major term (sadhya).
Ø Invariable concomitance: Vyapti or avinabhavaniyama, it is the nerve of inference.
Ø Paksadharmatā: the presence of the middle term (hetu) in the minor term.
Ø Vyapti: invariable association of middle term with the major term (sadhya)
Ø Paramarsa: Inference is knowledge arising through paramarsa. The knowledge of paksadharmata qualified by vyapti.
Ø Major term is sadhya, minor term is paksa and linga and middle term is hetu.
Ø Indian logic does not separate deduction from induction.
Ø Inference is of two types:
i. Svartha anumana: for one self
ii. Parartha anumana: for others.
Ø Syllogism: Nyaya syllogism is deductive inductive and formal-material. There are five syllogism in Nyaya logic:
i. Pratijna: this hill has fire
ii. Hetu: because it has smoke
iii. Udaharana: whatever has smoke has fire.
iv. Upanaya: this hill has smoke which is invariably associated with fire.
v. Naigama: therefore this hill has fire
Ø Truth in Nyaya inference is from particular to particular through universal.
Ø Characteristics of hetu (middle term):
i. It must be present in the minor term
Ø In Indian logic fallacy is hetvabhasa- It means middle term appears to be a reason but it is not a valid reason. It is of five kinds:
i. Asiddha or sadhyasama: it is divided into three parts:
ii. Savyabhichara: it is also divided into three parts:
Ø Gotama speaks of three kinds of inference:
i. Purvavat: based on causation.
ii. Shesavat: based on causation
iii. Samanyatodrsta: based on mere co-existence.
Ø Another classification of Inference divides inference into three parts:
Ø Verbal testimony is of two kids- vaidika and secular. There are a certain conditions for verbal testimony:
i. Akansa (expectancy)
ii. Yogyata (non-contradictory)
iii. Sannidhi (continuity)
iv. Tatparya (intention)
Ø Arthapatti or implication is reduced to inference in Nyaya philosophy. Abhava is reduced either to perception or inference.
Ø Comparison (upamiti): its means or source is called upamana. Comparison is the knowledge of the relation between a word and its denotation.
Ø Sabda: its means or source is also called sabda. Sabda as a source of valid knowledge is agam (the statement of a trustworthy person- aptavakya).
Ø Causation: a cause is defined as an unconditional and invariable antecedent of an effect and an effect as an unconditional and invariable consequent of a cause. The same cause produces the same effect and the same effect is produced by the same cause. There are a few essential characteristics of cause:
Ø Nyaya definition of a cause is the same as that in western inductive logic. Hume defines a cause as an invariable antecedent.
Ø Nyaya believes in teleological creation like vaisesika.
Ø Material cause of this universe: earth, water, fire and air.
Ø Efficient cause is god.
Ø Nyaya advocates:
Ø Creation is through combination of atoms and destruction is means dissolution of these combinations.
Ø Asatkaryavada: Nyaya view of causation because the different combinations of atoms are regarded as new creations, as real fresh bignning. This view implies that the effect does not preexist in the cause, it is a new begnning also known as arambhbhava.
Ø Soul; real knower, real enjoyer, real active agent, and an eternal substance.
Ø Nyaya accepts the metaphysics of vaisesika.