Nyāya (Sanskrit ni-āyß, literally "recursion", used in
the sense of "syllogism, inference") is the name given
to one of the six orthodox or astika schools of Hindu
philosophy—specifically the school of logic. The Nyaya
school of philosophical speculation is based on texts
known as the Nyaya Sutras, which were written by
Aksapada Gautama from around the 2nd century CE.
The most important contribution made by the Nyaya school
to modern Hindu thought is its methodology. This
methodology is based on a system of logic that,
subsequently, has been adopted by the majority of the
other Indian schools, orthodox or not. This is
comparable to how Western science and philosophy can be
said to be largely based on Aristotelian logic.
However, Nyaya differs from Aristotelian logic in that
it is more than logic in its own right. Its followers
believed that obtaining valid knowledge was the only way
to obtain release from suffering. They therefore took
great pains to identify valid sources of knowledge and
to distinguish these from mere false opinions. Nyaya is
thus a form of epistemology in addition to logic.
According to the Nyaya school, there are exactly four
sources of knowledge (pramanas): perception, inference,
comparison, and testimony. Knowledge obtained through
each of these can, of course, still be either valid or
invalid. As a result, Nyaya scholars again went to great
pains to identify, in each case, what it took to make
knowledge valid, in the process creating a number of
explanatory schemes. In this sense, Nyaya is probably
the closest Indian equivalent to contemporary analytic
 Sixteen padarthas or categories
The Nyaya metaphysics recognizes sixteen padarthas or
categories and includes all six (or seven) categories of
the Vaisheshika in the second one of them, called
prameya. These sixteen categories are pramāṇa (valid
means of knowledge), prameya (objects of valid
knowledge), saṁśaya (doubt), prayojana (aim), dṛṣṭānta
(example), siddhānta (conclusion), avayava (members of
syllogism), tarka (hypothetical reasoning), nirṇaya
(settlement), vāda (discussion), jalpa (wrangling),
vitaṇḍā (cavilling), hetvābhāsa (fallacy), chala
(quibbling), jāti (sophisticated refutation) and
nigrahasthāna (point of defeat).
The Nyaya epistemology considers knowledge (j˝āna) or
cognition (buddhi) as apprehension (upalabdhi) or
consciousness (anubhava). Knowledge may be valid or
invalid. The Naiyayikas (the Nyaya scholars) accepted
four valid means (pramaṇa) of obtaining valid knowledge
(prama) - perception (pratyakṣa), inference (anumāna),
comparison (upamāna) and verbal testimony (śabda).
Invalid knowledge includes memory (smṛti), doubt (saṁśaya),
error (viparyaya) and hypothetical reasoning (tarka).
Pratyakṣa (perception) occupies the foremost position in
the Nyaya epistemology. Perception is defined by
Akṣapāda Gautama in his Nyaya Sutra (I,i.4) as a
'non-erroneous cognition which is produced by the
intercourse of sense-organs with the objects, which is
not associated with a name and well-defined'. Perception
can be of two types, laukika (ordinary) and alaukika
Ordinary (Laukika or Sadharana) perception is of six
types - visual-by eyes, olfactory-by nose, auditory-by
ears, tactile-by skin, gustatory-by tongue and mental-by
Extraordinary (Alaukika or Asadharana) perception is of
three types, viz., Samanyalakshana (perceiving
generality from a particular object), J˝analakshana
(when one sense organ can also perceive qualities not
attributable to it, as when seeing a chili, one knows
that it would be bitter or hot), and Yogaja (when
certain human beings, from the power of Yoga, can
perceive past, present and future and have supernatural
abilities, either complete or some).
 Determinate and indeterminate perception
The Naiyayika maintains two modes or stages in
perception. The first is called nirvikalpa
(indeterminate), when one just perceives an object
without being able to know its features, and the second
savikalpa (determinate), when one is able to clearly
know an object. All laukika and alaukika pratyakshas are
savikalpa, but it is necessarily preceded by an earlier
stage when it is indeterminate. Vātsāyana says that if
an object is perceived with its name we have determinate
perception but if it is perceived without a name, we
have indeterminate perception. Jayanta Bhatta says that
indeterminate perception apprehends substance, qualities
and actions and universals as separate and indistinct
something and also it does not have any association with
name, while determinate perception aprrehends all these
together with a name. There is yet another stage
called Pratyabhij˝ā, when one is able to re-recognise
something on the basis of memory.
Anumāna (inference) is one of the most important
contributions of the Nyaya. It can be of two types:
inference for oneself (Svarthanumana, where one does not
need any formal procedure, and at the most the last
three of their 5 steps), and inference for others (Parathanumana,
which requires a systematic methodology of 5 steps).
Inference can also be classified into 3 types: Purvavat
(inferring an unperceived effect from a perceived
cause), Sheshavat (inferring an unperceived cause from a
perceived effect) and Samanyatodrishta (when inference
is not based on causation but on uniformity of
co-existence). A detailed anaysis of error is also
given, explaining when anumana could be false.
Upamāna, which can be roughly translated as comparison
is the knowledge of the relationship between a word and
the object denoted by the word. It is produced by the
knowledge of resemblance or similarity, given some
pre-description of the new object beforehand.
Śabda or verbal testimony is defined as the statement of
a trustworthy person (āptavākya), and consists in
understanding its meaning. It can be of two types,
Vaidika (Vedic), which are the words of the four sacred
Vedas, and are described as the Word of God, having been
composed by God, and Laukika, or words and writings of
trustworthy human beings. while Vaidika testimony is
perfect because the Vedas are spoken by God, Laukika
testimony are is not infallible.
Theory of inference
The methodology of inference involves a combination of
induction and deduction by moving from particular to
particular via generality. It has five steps, as in the
* There is fire on the hill (called Pratij˝ā, required
to be proved)
* Because there is smoke there (called Hetu, reason)
* Wherever there is smoke, there is fire, e.g. in a
kitchen (called Udāhārana, example of vyāpti)
* The hill has smoke that is pervaded by fire (called
Upanaya, reaffirmation or application)
* Therefore there is fire on the hill (called Nigamana,
In Nyāya terminology for this example, the hill would be
called as paksha (minor term), the fire is called as
sādhya (major term), the smoke is called as hetu, and
the relationship between the smoke and the fire is
called as vyāpti(middle term). Hetu further has five
characteristics: (1) It must be present in the Paksha,
(2) It must be present in all positive instances, (3) It
must be absent in all negative instances, (4) It must
not incompatible with the minor term or Paksha and (5)
All other contradictions by other means of knowledge
should be absent.
The fallacies in Anumana (hetvābhasa) may occur due
to the following:
1. Asiddha: It is the unproved hetu that results in this
* Ashrayasiddha: If Paksha [minor term] itself is
unreal, then there cannot be locus of the hetu. e.g. The
sky-lotus is fragrant, because it is a lotus like any
* Svarupasiddha: Hetu cannot exist in paksa at all. E.g.
Sound is a quality, because it is visible.
* Vyapyatvasiddha: Conditional hetu. `Wherever there is
fire, there is smoke'. The presence of smoke is due to
2. Savyabhichara: This is the fallacy of irregular hetu.
* Sadharana: The hetu is too wide. It is present in both
sapaksa and vipaksa. `The hill has fire because it is
* Asadharana: The hetu is too narrow. It is only present
in the Paksha, it is not present in the Sapaksa and in
the Vipaksha. `Sound is eternal because it is audible'.
* Anupasamhari: Here the hetu is non-exclusive. The hetu
is all-inclusive and leaves nothing by way of sapaksha
or vipaksha. e.g. 'All things are non-ternal, because
they are knowable'.
3. Satpratipaksa: Here the hetu is contradicted by
another hetu. If both have equal force, then nothing
follows. 'Sound is eternal, because it is audible', and
'Sound is non-eternal, because it is produced'. Here
'audible' is counter-balanced by 'produced' and both are
of equal force.
4. Badhita: When another proof (as by perception)
definitely contradicts and disproves the middle term (hetu).
'Fire is cold because it is a substance'.
5. Viruddha: Instead of proving something it is proving
the opposite. 'Sound is eternal because it is produced'.
The Nyaya theory of 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. The cause is not present
in any hidden form whatsoever in its effect.
The following conditions should be met:
1. The cause must be antencedent [Purvavrtti]
2. Invariability [Niyatapurvavrtti]
3. Unconditionality [Ananyathasiddha]
Nyaya recognizes five kinds of accidental antecedents [Anyathasiddha]
1. Mere accidental antecedent. E.g., The colour of the
2. Remote cause is not a cause because it is not
unconditional. E.g., The father of the potter.
3. The co-effects of a cause are not causally related.
4. Eternal substances, or eternal conditions are not
unconditional antecedents. e.g. space.
5. Unnecessary things, e.g. the donkey of the potter.
Nyaya recognizes three kinds of cause:
1. Samavayi, material cause. E.g. Thread of a cloth.
2. Asamavayi, colour of the thread which gives the
colour of the cloth.
3. Nimitta', efficient cause, e.g. the weaver of the
Anyathakyativada of Nyaya
The Nyaya theory of error is similar to that of
Kumarila's Viparita-khyati (see Mimamsa). The Naiyayikas
also believe like Kumarila that error is due to a wrong
synthesis of the presented and the represented objects.
The represented object is confused with the presented
one. The word 'anyatha' means 'elsewise' and 'elsewhere'
and both these meanings are brought out in error. The
presented object is perceived elsewise and the
represented object exists elsewhere. They further
maintain that knowledge is not intrinsically valid but
becomes so on account of extraneous conditions (paratah
pramana during both validity and invalidity).t
Nyaya argument for the existence of God
Early Naiyayikas wrote very little about God, i.e.,
Ishvara (literally, the Supreme Lord). However, later
Buddhists in India had become from agnostic to strictly
atheistic. As a reaction, the later Naiyayikas entered
into disputes with the Buddhists and tried to prove the
existence of God through logic. They made this question
a challenge to their own existence. They gave the
following nine proofs for the existence of God, enlisted
in Udayana's Nyaya Kusumanjali:
* Kāryāt (lit. "from effect"): An effect is
produced by a cause, and similarly, the universe must
also have a cause. Causes (according to Naiyayikas) are
of three kinds: Samavayi (in case of the universe, the
atoms), Asamavayi (the association of atoms) and Nimitta
(which is Ishvara). The active cause of the world must
have an absolute knowledge of all the material of
creation, and hence it must be God. Hence from the
creation, the existence of the Creator is proved.
* Āyojanāt (lit., from combination): Atoms are
inactive and properties are unphysical. So it must be
God who creates the world with his will by causing the
atoms to join. Self-combination of inanimate and
lifeless things is not possible, otherwise atoms would
only combine at random, creating chaos. There is to be
seen the hand of a wise organizer behind the systematic
grouping of the ultimate atoms into dyads and molecules.
That final organizer is God.
* DhŗitÚ(lit., from support): Just as a material
thing falls off without a support, similarly, God is the
supporter and bearer of this world, without which the
world would not have remained integrated. This universe
is hence superintended within God, which proves his
* Padāt (lit., from word): Every word has the
capability to represent a certain object. It is the will
of God that a thing should be represented by a certain
word. Similarly, no knowledge can come to us of the
different things here unless there is a source of this
knowledge. The origin of all knowledge should be
omniscient and, consequently, omnipotent. Such a being
is not to be seen in this universe, and so it must be
outside it. This being is God.
* Pratyatah (lit, from faith): the Hindu holy
scriptures, the Vedas, are regarded as the source of
eternal knowledge. Their knowledge is free from
fallacies and are widely believed as a source of proof.
Their authors cannot be human beings because human
knowledge is limited. They cannot obtain knowledge of
past, present, and future, and in depth knowledge of
mind. Hence, only God can be the creator of the Vedas.
Hence, his existence is proved from his being the author
of the Vedas, which he revealed to various sages over a
period of time.
* ShrutÚh (lit., from scriptures): The Shrutis,
e.g., the Vedas extol God and talk about his existence.
"He is the lord of all subjects, omniscient, and knower
of one's internal feelings; He is the creator, cause and
destroyer of the world", say the Shrutis. The Shrutis
are regarded as a source of proofs by Naiyanikas. Hence,
the existence of God is proved.
* Vākyāt (lit., from precepts): Again, the Veda
must have been produced by a person because it has the
nature of "sentences," i.e., the sentences of the Veda
were produced by a person because they have the nature
of sentences, just as the sentences of beings like
ourselves. That person must have been God.
* Samkhyāvişheshāt (lit., from the specialty of
numbers): The size of a dyad or a molecule depends on
the number of the atoms that constitute it. This
requisite number of the atoms that form a particular
compound could not have been originally the object of
the perception of any human being; so its contemplator
must be God.
* Adŗişhţāt (lit., from the unforeseen): It is
seen that some people in this world are happy, some are
in misery. Some are rich, and some are poor. The
Naiyanikas explain this by the concept of Karma and
reincarnation. The fruit of an individual's actions does
not always lie within the reach of the individual who is
the agent. There ought to be, therefore, a dispenser of
the fruits of actions, and this supreme dispenser is
Nyaya arguments for monotheism
Not only have the Naiyanikas given proofs for the
existence of God, but they have also given an argument
that such a God can only be one. In the Nyaya
Kusumanjali, this is discussed against the proposition
of the Mimamsa school—that let us assume there were many
demigods (Devas) and sages (rishis) in the beginning,
who wrote the Vedas and created the world. Nyaya says
[if they assume such] omniscient beings, those endowed
with the various superhuman faculties of assuming
infinitesimal size, and so on, and capable of creating
everything, then we reply that the law of parsimony bids
us assume only one such, namely Him, the adorable Lord.
There can be no confidence in a non-eternal and non
omniscient being, and hence it follows that according to
the system which rejects God, the tradition of the Veda
is simultaneously overthrown; there is no other way
In other words, Nyaya says that the polytheist would
have to give elaborate proofs for the existence and
origin of his several celestial spirits, none of which
would be logical. So it is much more logical to assume
only One, eternal and omniscient God.
Literature of Nyaya
The earliest text of the Nyaya School is the Nyāya Sūtra
of Akṣapāda Gautama. The text is divided into five
books, each having two sections. Vātsāyana’s Nyāya
Bhāṣya is a classic commentary on the Nyāya Sūtra.
Udyotakara’s Nyāya Vārttika (6th century CE) is written
to defend Vātsāyana against the attacks made by Dignāga.
Vācaspati Miśra’s Nyāyavārttikatātparyaṭīkā (9th century
CE) is the next major exposition of this school. Two
other texts, Nyāyaṣūcinibandha and Nyāyasūtraddhāra are
also attributed to him. Udayana’s (984 CE)
Nyāyatātparyapariśuddhi is an important commentary on
Vācaspati’s treatise. His Nyāyakusumā˝jali is the first
systematic account of theistic Nyāya. His other works
include Ātmatattvaviveka, Kiraṇāvali and Nyāyapariśiṣṭa.
Jayanta Bhatta’s Nyāyama˝jari (10th century CE) is
basically an independent work. Bhāsavaraj˝a’s Nyāyasāra
(10th century CE) is a survey of Nyāya philosophy).
The later works on Nyāya accepted the Vaiśeṣika
categories and Varadarāja’s Tārkikarakṣā (12th century
CE) is a notable treatise of this syncretist school.
Keśava Miśra’s Tārkabhaṣā (13th century CE) is another
important work of this school.
Gangeśa Upādhyāya’s Tattvacintāmaṇi (12th century CE) is
the first major treatise of the new school of Navya
Nyāya. His son, Vardhamāna Upādhyāya’s
Nyāyanibandhaprakāśa (1225 CE), though a commentary on
Udayana’s Nyāyatātparyapariśuddhi, incorporated his
father’s views. Jayadeva wrote a commentary on
Tattvacintāmaṇi known as Āloka (13th century CE).
Vāsudeva Sārvabhauma’s Tattvacintāmaṇivyākhyā (16th
century CE) is first great work of Navadvipa school of
Navya Nyāya. Raghunātha Śiromaṇi’s
Tattvacintāmaṇidīdhiti and Padārthakhaṇḍana are the next
important works of this school. Viśvanatha’s
Nyāyasūtravṛtti (17th century CE) is also a notable
work. The Commentaries on Tattvacintāmaṇidīdhiti by
Jagadish Tarkalankar (17th century CE) and Gadadhar
Bhattacharya (17th century CE) are the last two notable
works of this school.
Ānnaṁbhatta (17th century CE) tried to develop a
consistent system by combining the ancient and the new
schools, Prācina nyāya and Navya nyāya and Vaiśeṣika to
develop the nyāya-vaiśeṣika school. His Tarkasaṁgraha
and Dīpikā are the popular manuals of this school.