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2. Nyaya: The Philosophy of Logic and Reasoning

The nyaya system of philosophy was established by the sage Gautama. As he was also known as Aksapada, this system is also sometimes referred to as the aksapada system. Nyaya philosophy is primarily concerned with the conditions of correct knowledge and the means of receiving this knowledge. Nyaya is predominantly based on reasoning and logic and therefore is also known as Nyaya Vidya or Tarka Sastra -- "the science of logic and reasoning." Because this system analyzes the nature and source of knowledge and its validity and nonvalidity, it is also referred to as anviksiki, which means "the science of critical study." Using systematic reasoning, this school of philosophy attempts to discriminate valid knowledge from invalid knowledge.

This philosophy asserts that obtaining valid knowledge of the external world and its relationship with the mind and self is the only way to attain liberation. If one masters the logical techniques of reasoning and assiduously applies these in his daily life, he will rid himself of all suffering. Thus, the methods and conditions of determining true knowledge are not the final goal of nyaya philosophy; logical criticism is viewed only as an instrument that enables one to discriminate valid from invalid knowledge. The ultimate goal of nyaya philosophy, like that of the other systems of Indian philosophy, is liberation -- the absolute cessation of pain and suffering. Nyaya is a philosophy of life, even though it is mainly concerned with the study of logic and epistemology.

All six schools of Vedic philosophy aim to describe the nature of the external world and its relationship to the individual, to go beyond the world of appearances to ultimate Reality, and to describe the goal of life and the means for attaining this goal. In this attempt, the six philosophies divide their course of study into two major categories: the study of unmanifested reality, and the study of manifest reality. In nyaya philosophy, both aspects of reality are divided into sixteen major divisions, called padarthas (see chart below). These sixteen philosophical divisions are: pramana, the sources of knowledge; prameya, the object of knowledge; samsaya, doubt or the state of uncertainty; prayojana, the aim; drstanta, example; siddhanta, doctrine; ayayava, the constituents of inference; tarka, hypothetical argument; nirnaya, conclusion; badha, discussion; jalpa, wrangling; vitanda, irrational argument; hetvabhasa, specious reasoning; chala, unfair reply; jati, generality based on a false analogy; and nigrahsthana, the grounds for defeat. The subjects discussed under pramana, the source of knowledge, are the most important and the most thoroughly and profoundly expounded of all the divisions. For this reason, pramana will be explained in detail after the other fifteen divisions of studying reality have been described.

Nyaya's Sixteen Divisions (Padarthas) of Studying Reality

I. Pramana, four sources of valid knowledge (prama):

o 1. Perception (pratyaksa)

Ordinary (laukika)

Indeterminate (nirvikalpa)

Extraordinary (alaukika)

Classes (samanyalaksana)

Association (jnanalaksana)

Intuition (yogaja)

o 2. Inference (anumana)

Statements (pratijna)

Reason (hetu)

Example (udaharana)

Universal proposition (upanaya)

Conclusion (nigamana)

o 3. Comparison (upamana)

o 4. Testimony (sabda)

II. Prameya, twelve objects of knowledge:

o Atman

o The body

o The five senses

o The objects of the senses

o Cognition

o Mind

o Activity

o Mental defects (attachment, hatred, and infatuation)

o Rebirth

o Results

o Suffering

o Freedom from suffering.

III. Doubt (samsaya)

IV. Aim (prayojana)

V. Example (drstanta)

VI. Doctrine (siddhanta)

VII.Constituents of inference (five avayavas)

VIII. Hypothetical argument (tarka)

IX. Conclusion (nirnaya)

X. Discussion (badha)

XI. Wrangling (jalpa)

XII. Irrational reasoning (vitanda)

XIII. Specious reasoning (hetvabhasa)

XIV. Unfair reply (chala)

XV. Generality based on a false analogy (jati)

XVI. Grounds for defeat (nigrahasthana)

The Object of Knowledge. Prameya may be translated as "that which is knowable," or "the object of true knowledge." That which is the object of cognition is prameya, and whatever is comprehended or cognized by buddhi is categorized into the twelve objects of cognition known as the prameyas. These twelve divisions are: atman, the self; sarira, the body -- the abode of the experience of pain and pleasure that is the seat of all organic activities; indriyas, the five senses -- smell, taste, sight, touch and hearing -- which contact external objects and transmit the experience to the mind; artha, the objects of the senses; buddhi, cognition; manas, the mind -- the internal sense that is concerned with the perception of pleasure, pain, and all other internal experiences and that, according to nyaya, limits cognition to time and space. The mind is compared to an atom (not the atom of modern physics; see vaisesika philosophy) because it is minute, everlasting, individual, and all-pervading; pravrtti, activity -- vocal, mental, and physical; dosa, mental defects that include attachment (raga), hatred (dvesa), and infatuation or delusion (moha); pretyabhava, rebirth or life after death; phala, the fruits or results of actions experienced as pain or pleasure; dukha, suffering -- the bitter or undesired experiences of mind; and apavarga, liberation or complete cessation of all suffering without any possibility of its reappearance.

According to nyaya philosophy the goal of life is to understand these twelve aspects of reality, the prameyas, as they actually are. Bondage is born of the isunderstanding of these twelve knowable objects, and one obtains freedom from bondage when he attains the correct know ledge of these twelve aspects of reality. Most of the time, however, this knowledge remains incomplete, and the means for attaining an integral comprehension of reality is not learned, so defective or invalid knowledge is maintained. In order to cast off this invalid knowledge, nyaya provides a profound method for determining valid knowledge. This is studies under the category of pramana, which will be discussed following brief descriptions of the other fourteen components in the nyaya process for attaining valid knowledge.

Doubt. Samsaya means "doubt." It is the state in which the mind wavers between conflicting views regarding a single object. In a state of doubt, there are at least two alternative views, neither of which can be determined to lead to a state of certainty. Samsaya is not certain knowledge; neither is it a mere reflection of knowledge; nor is it invalid knowledge. It is a positive state of cognition, but the cognition is split in two and does not provide any definite conclusions. For example, in the dark of the night a person may be looking at a plant, but because he cannot see clearly he does not recognize the p]ant for what it is and falsely perceives it as a man. However, if it would be logically impossible for a man to be present at that place, then the mind does not accept that the figure is a man. The mind becomes confused at that moment, questions whether it is a man or a plant, and cannot come to a decision about what it actually is. Thus, doubt is a product of a confused state of mind that is not able to perceive with clarity.

Aim. The word prayojana means "aim." Without an aim or a target, no one can perform any action. It does not matter whether that aim is fully understood or just presumed. One acts either to achieve desirable objects or to get rid of undesirable ones; these desirable and undesirable objects that motivate one's activities are known as prayojana.

Example. Drstanta is the use of an example to illustrate a common fact and establish an argument. This is a very important aspect of reasoning, for frequently a useful example can be accepted by both parties involved in a discussion without any disputation or difference of opinion. For instance, when one argues that there must be fire because there is smoke, he may use the example of smoke in the kitchen to confirm the permanent relationship between fire and smoke. The relationship between fire and smoke in the kitchen is a common occurrence and may be readily accepted by both parties. Therefore, the example of the kitchen for confirming the existence of fire inferred from the presence of smoke is potentially very helpful.

Doctrine. Siddhanta means "doctrine." It is an axiomatic postulate that is accepted as the undisputed truth and that serves as the foundation for the entire theory of a particular system of philosophy. This accepted truth might be derived either from direct experience or from reasoning and logic. For example, it is the doctrine of nyaya philosophy that there is a God (nimitta karana) who is the operative cause of the universe and who organizes and regulates the atoms.

Constituents of inference. The term avayaya literally means "constituents" or "parts," and in this context it refers to the constituents of inference. This is an important topic in nyaya philosophy because nyaya strongly emphasizes describing the minute complexities of the pramanas, the sources or methods of receiving correct knowledge. Among these methods, inference is the most important source of correct knowledge, and nyaya therefore provides a technical method to test the validity of inference. If an inference contains five necessary constituents, then it can give correct know ledge. These five requisite components of inference are pratijna (statements); hetu (reason); udaharana (example); upanaya (universal proposition); and nigamana (conclusion). These are discussed later in this chapter in the section on inference.

Hypothetical argument. Tarka may be translated as "hypothetical argument." All the systems of Indian philosophy agree that it is simply the mind's jabbering that creates confusion and misunderstanding within and without. Because the mind is clouded by its own modifications, it is very important to wash out these confusions before attempting to understand something solely through the mind. For this purpose, nyaya philosophy discusses the possible problems of the mind and clarifies its confusions, using such processes as tarka. Tarka is the process of questioning and cross-questioning that leads to a particular conclusion. It is a form of supposition that can be used as an aid to the attainment of valid knowledge. Tarka can become a great instrument for analyzing a common statement and for discriminating valid knowledge from invalid knowledge.

Conclusion. Nirnaya, conclusion, is certain knowledge that is attained by using legitimate means. If the mind has doubts concerning the correctness or validity of a conclusion it has drawn, then employing the process of tarka (hypothetical argument) can help to resolve those doubts. But it is not always necessary for a conclusion to pass through a doubtful state. It may be indubitably perceived, either through direct perception, inference, testimony, or intuition. Nirnaya is this ascertainment of assured truth about something that is attained by means of recognized and legitimate sources of knowledge.

Discussion. Badha, discussion, is a kind of debate between two parties -- the exponent and the opponent -- on a particular subject. Each party tries to establish its own position and to refute that of the other, arguing against any theory propounded by the other. Both, however, are trying to arrive at the truth by applying the methods of reasoning and logic. This is an effective and efficient way to reach valid knowledge if both parties are honest and free from prejudices.

Wrangling. Jalpa, or wrangling, is the process by which the exponent and opponent both try to attain victory over the other without making an honest attempt to come to the truth; there is an involvement of ego instead of a search for knowledge. Jalpa contains all the characteristics of a valid debate except that of aiming to discover truth. It is that type of discussion in which each party has a prejudice for his own view and thus tries to gather all possible arguments in his own favor. Lawyers sometimes apply this method to win their cases in court.

Irrational reasoning. Vitanda is irrational reasoning. Specifically, it is argumentation that is aimed exclusively at refuting or destroying an antagonist's position and that is not at all concerned with establishing or defending one's own position. It is mere destructive criticism of the views of one's opponent. Whereas in wrangling both the exponent and opponent try to establish their own position, in irrational reasoning either or both tries to refute the other's position instead of establishing his own. This usually occurs when one or both parties realize that his own case is weak and that he cannot defend his point of view. Consequently, he irrationally attacks the other's case with destructive intent.

Specious reasoning. Hetvabhasa means "irrational argument." It is reasoning that appears to be valid but is really unfounded. This specious reasoning is a fallacy of inference, and it is therefore discussed later in this chapter in the section on inference.

Unfair reply. Chala means "unfair reply." Here it is used to designate a statement that is meant to cheat or to fool someone. In unfair reply one takes a word or phrase that has been used in a particular sense, pretends to understand it in a sense other than that which was intended, and then denies the truth of this deliberate misinterpretation of the original speaker's words. For example, suppose someone's name is Bizarre, and in referring to this person, someone says, "He is Bizarre." If the listener knowingly misconstrues this statement and replies, "He is not bizarre; he is just a common ordinary man," then that person is using chala.

Generality based on a false analogy. Jati means generality, but as used here,it is a technical term used to describe a debate in which an unfair reply or conclusion is based on a false analogy. Suppose, for example, that someone is arguing that sound is noneternal because it is an effect of a certain cause, just as a pot is produced from clay. But another argues that sound must be eternal because it is nonmaterial, like the sky. This counter argument of trying to prove the eternity of sound by comparing it with the nonmaterial sky is fallacious, because there is not necessarily a universal relationship between the nonmaterial and the eternal. (In the nyaya system itself, sound is considered to he a noneternal quality because it is produced and can be destroyed. Some other systems, however, do not agree with this view.)

Grounds for defeat. Nigrahasthana may be translated as "the grounds on which a person is defeated in his argument." When a proponent misunderstands his own or his opponent's premises and their implications, then he becomes helpless and must eventually admit his defeat in the debate. The point at which he accepts his defeat is called nigrahasthana.

Pramana -- The Sources of Valid Knowledge

Pramana is that through which or by which the prama (valid knowledge) is received. It is the last of nyaya's philosophical divisions to be discussed. There are four distinct fountains of correct knowledge. These four pramanas are: perception (pratyaksa); inference (anumana); comparison (upamana); and testimony (sabda). Before discussing these sources of knowledge, the nature or definition of knowledge should first be examined and the method for distinguishing correct knowledge from false knowledge should be determined.

In nyaya philosophy, knowledge is divided into two major categories, anubhava (experiential knowledge) and smrti (memory). Experiential knowledge is received through the four pramanas mentioned above -- perception, inference, comparison, and testimony. The second type of knowledge, that which is based on memory, is derived from the storehouse of one's own mind, but ultimately these memories also depend on experiential knowledge because no one can remember something that he has not experienced. During the process of remembering, a memory is called up from its storehouse and is then received as knowledge of an object. These two major categories of knowledge can be divided into two parts: valid and invalid. In the language of nyaya philosophy, valid experiential know]edge is called prama, and nonvalid experiential knowledge is called aprama. Prama can be received through perception, inference, comparison, and testimony; therefore there are four types of valid knowledge based on these four means. Aprama is divided into doubt (samsaya), faulty cognition (bhrama or viparyaya), and hypothetical argument (tarka). Certain and unerring cognition (such as the visual perception of a chair) is valid knowledge because the knowledge is presented directly to the senses as it really is. Memory is not original knowledge because it is not experiential; it is a mere reproduction of experiential knowledge. Knowledge based on memory may be either valid or invalid, depending on the correctness of the recollection of the experiential knowledge that occurred in the past. A doubtful cognition cannot be called valid (prama) because it is not definite knowledge. Faulty cognition likewise cannot be pramana because it is not true to the nature of its object. Tarka (hypothetical argument) cannot be called prama because in itself it is not knowledge. Although it may help in drawing some conclusions about a fact, it is only a means of attaining knowledge.

According to nyaya philosophy true knowledge is that which corresponds to the nature of its object; otherwise the knowledge is false. To perceive a thing in its true nature is true knowledge. For example, the knowledge of a red rose is true if the rose is really red, but the knowledge of a red rose as white is not true because the rose is not white. How can one know if the rose is truly red and not white? How is it possible to prove the validity or falsity of knowledge? Nyaya philosophy says that the validity or invalidity of knowledge depends on its correspondence or non-correspondence to the facts. For example, if one wants to have correct knowledge of sugar, one tastes it. If there is some powdery white crystal in the kitchen and one puts a pinch of it in his mouth thinking that it is sugar, he will be surprised and disappointed if he finds that it is salty and not sweet. But he will have certain knowledge that what he had thought to be sugar is instead salt. True knowledge leads a person to successful practical activity. while false knowledge makes one helpless and leads to failure and disappointment.


As mentioned earlier, according to nyaya there are four sources of valid experiential knowledge or prama -- perception, inference, comparison, and testimony -- among which perception is foremost. Most people believe that whatever is experienced through perception must be true, and they do not further test the data that are received via the senses. Nyaya philosophy, however, is very critical in this respect and makes a thorough examination of perception.

Perception is knowledge produced by the contact of the senses with the objects of the world. For example, one has perceptual knowledge of a table when a table comes in contact with the eyes. To be considered valid, the contact of the senses with their objects must be clear and doubtless. The perception of something a long distance away as being either a bush or a bear is a doubtful and indefinite cognition and is, therefore, not true perception. Mistakenly perceiving a rope as a snake may be neither doubtful nor indefinite, but it is a false and therefore invalid perception.

Nyaya philosophy has several different systems of classification of perception. According to the first kind of classification, there are two types of perceptions: laukika (ordinary) and alaukika (extraordinary). When a perception is derived from direct contact with a sense object, that is ordinary perception. When the object is not directly present to the senses but is conveyed to the senses through unusual modes, then that perception is called alaukika -- extraordinary. Modes of perception are either external (bahya) or internal (manasa). In external perception, any or all of the faculties of sight, hearing. touch, taste, and smell are involved in bringing the object to the mind. Thus, there are five kinds of external perceptions (bahya): visual, auditory, tactile, gustatory, and olfactory. The five senses of hearing. touching, seeing, tasting, and smelling are all gross senses. while mind is the subtle sixth sense. Mind is the internal faculty that perceives the qualities of soul such as desire, aversion, pleasure, pain, and cognition.

In nyaya philosophy, ordinary perception (laukika) is either indeterminate (nirvikalpa) or determinate (savikalpa). Indeterminate perception is the primary cognition of a thing before judgment is used to specify diverse characteristics. For example, in the first glance at a table, one perceives the mere existence of the table without comprehending its color, shape, and other specific characteristics; one perceives only a general appearance without details. Only upon further inspection does one recognize that it is, say, a round wooden table with a drop leaf. This determinate perception is the cognition of an object that registers some definite characteristics about it. Determinate perception is always preceded by indeterminate perception, and determinate perception is always valid knowledge because it is definite and explicit.

Nyaya claims that there are three kinds of extraordinary (alaukika) perceptions: perception of classes (samanya laksana); perception based on association (jnana laksana); and intuitive perception (yogaja). The realization that all people are mortal is an instance of the external perception of classes (samanya laksana). How does one know that all people are mortal? One cannot come to this realization by ordinary perception because the mortality of all people in all times cannot be physically perceived by the senses. But because a person is never perceived without his personhood -- that is, the class essence or universality all human beings share -- then a conclusion can be made based on that essence. A person is known as a person because of the presence of person hood in him. This direct perception of personhood is the medium through which all people, or the class of people, are perceived. To perceive personhood means to perceive all people as individuals in which this characteristic resides. The perception of all people is due to the perception of the universality of humanity in all people. Therefore, this type of knowledge is called the extraordinary perception of classes.

A different type of extraordinary perception -- jnana laksana (association) -- is involved when one says that something looks delicious, or that a block of ice looks cold, or that a stone looks hard. These assertions imply that the taste of food, the coldness of ice, and the hardness of stone can be perceived by the eyes. But how can the eyes perceive the qualities of taste and touch? Nyaya says that the past experience of touch and taste are so closely associated with the visual appearance of the causative agents of those experiences that whenever these sources come in contact with the eyes they bring about the perception of taste and touch simultaneously with that of their color. This present perception of taste and touch due to the revived past knowledge of the color of the food, ice, or stone is called jnana laksana -- perception based on association. This type of know]edge is extraordinary because it is conveyed by a sense organ that ordinarily is not capable of perceiving that type of knowledge. Because the mind incorporates previously associated experiences, it is able to perceive such knowledge.

The third kind of extraordinary perception is called yogaja, the knowledge born of yoga practices. It is intuitive knowledge that never depends on sense-object contact and is never false; it is perceived after the mind is cleansed through yogic practices. This knowledge from within is divided into two categories, depending on the degree of perfection of yogi attainments. Those who have completed their inward journey and have attained spiritual perfection, who perceive intuitive knowledge of all objects constantly and spontaneously, are called yukta yogins. Those who are still on the path of the spiritual journey, for whom concentration and other auxiliary conditions are required to attain an intuitive knowledge, are called yunjan yogins.


Nyaya philosophy provides a detailed and systematic description of inference. Inference is the process of knowing something not by means of contact between the senses and the objects of the world and not by observation but rather through the medium of a sign, or linga, that is invariably related to it. Inference involves the process of analyzing memories, correlations, and uncontaminated arguments. There is a systematic method for testing the validity of inferential knowledge, for there are always some inseparable constituents to an inference, and if any of these parts are missing or if there is any defect in the parts, then the knowledge inferred is invalid.

The Sanskrit word for inference is anumana, and may be defined as "the cognition or knowledge that follows from some other knowledge." Two examples are: "The hill is on fire because there is smoke on the hill, and where there is smoke there is fire," and "John is mortal because he is a man, and all men are mortal." In the first example, we perceive smoke on the hill and arrive at the knowledge of the existence of fire on the hill on the basis of our previous knowledge of the universal relationship between smoke and fire. In the second example, we begin with the perception of a man, John. which inspires the knowledge of the mortality of John based on our previous knowledge of the universal relationship between men and mortality. Thus, it is apparent that inference is a process of reasoning in which one passes through certain necessary stages to reach a conclusion, which is called inferential knowledge. The necessary stages are the conditions for a valid inference. In the process of inference, one reaches a conclusion regarding a particular fact through the knowledge of a sign and of the sign's universal relationship to the conclusion.

In the example of the inference of fire on a hill, one ascertains the presence of the unperceived fire on the hill through the perception of the smoke on the hill, because one a]ready has the knowledge of the universal relationship between smoke and fire. A primary condition of this inference is the knowledge of smoke on the hill; this part of the inferential process is called linga, or sign. Next arises the awareness of the universal relationship between smoke and fire based on past observations; this is known as vyapti. As a result of this, knowledge of the existence of the unperceived fire on the hill arises. This stage is called nirnaya or conclusion. In the terminology of logic, the hill is the minor term paksa) in this inference because the hill is the subject under consideration. Fire is the major term (sadhya) because this is what we want to prove in relation to the hill. The presence of smoke on the hill is the middle term (linga) because it is the sign that indicates the presence of fire. This middle term is also called hetu or sadhana, meaning "the reason or grounds for inference."

Three parts of inference. Thus, an inference contains three parts: the minor term (paksa), the major term (sadhya), and the middle term (hetu or linga). In the process of inference, the first step is the apprehension of smoke (hetu) on the hill (paksa); the second step is the recollection of the universal relationship between smoke and fire (hetu and sadhya); and the third step is the cognition of fire (sadhya). When used as a formal statement or verbal expression designed to convince others, however, the structure of inference is changed. In stating an inferential verbal expression for others, the first step will be the predication of the major term in relation to the minor term: "There is fire on the hill." The second step will be the formation of the middle term in relation to the minor term: "There is visible smoke on the hill." The third step will be the formation of the middle term in its universal or invariable relationship with the major term: "Where there's smoke, there's fire." In this last step it is sometimes helpful to use a specific example to confirm the relationship between the middle term and major term. For instance, "Where there's smoke there's fire, as in the kitchen."

Thus, inference may be said to be a syllogism consisting of at least three categorical premises. But when one is analyzing the whole process of an inference, and especially when one is using inference to prove or demonstrate something, then it is necessary to state the inference in a systematic and comprehensive chain of arguments. One must then state a syllogism in the form of five premises. These five premises (avayavas) that constitute a valid inference are pratijjna (fact); hetu (reasons); udaharana (example); upanaya (application); and nigamana (conclusion). Here is an example: (1) John is mortal (fact); (2) Because he is a man (reason); (3) All men are mortal -- for example, Napoleon, Lincoln, Socrates, and so on (example); (4) John is a man (application); (5) Therefore John is mortal (conclusion). The first premise states a positive fact. The second premise states the reason for this assertion. The third premise then confirms the relationship between the reason for the assertion and the asserted fact itself as supported by a well-known example. The fourth constituent of the syllogism represents the application of the universal proposition to the present case. The fifth part, or conclusion, is drawn from the preceding four parts.

To gain a proper understanding of the workings of logic, it is necessary to examine more closely how a systematic syllogism functions. For this purpose, the following example may be reanalyzed. "There is fire on the hill because there is smoke, and where there is smoke, there is fire." As was previously discussed, fire is the major term, hill is the minor term, and smoke is the middle term. The middle term (smoke) is so-called because, on the one hand, it is connected to the minor term (hill), and, on the other hand, it is universally related to the major term (fire). This middle term is also called reason or grounds since it is because of its perception that the major term is inferred. Thus, an inference has two conditions: the knowledge of the middle term must exist in the minor term; and a relationship must exist between the middle and the major terms. It is not possible to realize the existence of fire on the hill as a conclusion based on inferential reasoning if the invariable concomitance between the middle and major terms is not established. This invariable concomitance between these two terms of an inference is called vyapti, the logical ground for inference. Concomitance guarantees the validity of the conclusion; the validity or invalidity of an inference depends on the validity or invalidity of vyapti. Therefore, nyaya philosophy goes into great detail concerning the nature of concomitance and the fallacies related to it.

Logical ground for inference. Vyapti, meaning "the state of pervasiveness," implies both that which pervades and that which is pervaded. For example, in the inference of fire and smoke, smoke is the pervaded and fire is the pervader. Here smoke is always accompanied by fire -- wherever there is smoke, there will also be fire. The reverse, however, is not necessarily true: it is possible to have fire without smoke -- for example, a Bunsen burner. But there are examples in which both the pervader and the pervaded coexist permanently -- for example, fire and heat. There are, therefore, two kinds of concomitance: equivalent and nonequivalent. Nonequivalent concomitance (asamavyapti) is an invariable concomitance between two unequal entities (such as smoke and fire). It has already been shown that in this type of concomitance, one entity may be inferred from the other, but not vice versa. Equivalent vyapti (samuvyapti) is an invariable concomitance between two coexistent terms, either of which can be inferred from the other. For example, a chair is a nameable thing because a chair is knowable, and whatever is knowable, is nameable. Here nameable and knowable can both be inferred from each other.

Concomitance denotes a relationship of coexistence (sahacarla). But not every instance of coexistence is an example of concomitance. Fire, for example, often coexists with smoke, yet it may exist without smoke. The coexistent relationship of fire and smoke depends on certain conditions -- temperature and wetness, for instance. The condition on which the relation of coexistence depends is called upadhi, and for an inference to be valid, the relation between the middle and major terms of a syllogism must be independent of any and all conditions. In other words, a valid concomitance represents an invariable and unconditional concomitant relation (nitya anaupadika sambandha) between the middle and major terms of a syllogism.

But how does one know that a relation is invariable and unconditional? Vedantins reply that concomitance is established by the uncontradicted experiences of the relationships between two things. But according to nyaya, concomitance is established through the perception of classes (samanya laksana perception), which has been discussed earlier in this chapter in the section on extraordinary perceptions. Actually, the nyaya method of inference uses inductive reasoning; that is, it draws a particular conclusion on the grounds of a general and universally known truth. The universal truth is considered to fall within the range of vyapti. In nyaya, there are three types of inductive analysis, or generalization. The first is anvaya, or uniform agreement in presence. This type of inductive process arises from observing a relationship in which if one constituent is present, then in every instance the other constituent is also present -- for example, wherever there is smoke there is fire. The second type of inductive analysis is the obverse of the first, and is called uniform agreement in absence (vyatireka). In this method, a negative universal relationship or invariable concomitance is observed -- for example, wherever there is no fire, there is no smoke. The third kind of inductive process is a combination of the first and second methods. In this method, known as uniform agreement in both presence and absence (anvaya-vyatireka or vyabhicaragraha), both constituents of a relationship are always found together; neither is ever present without the other. From this, it is induced that there must exist a natural relationship of invariable concomitance between them.

These three methods of generalization demonstrate a systematic technique for inductive reasoning. The most crucial concern, however, in any systematic inference is how to make certain that concomitance, the logical basis for the inference, is valid -- that is, free from limiting conditions (upadhis). This process of insuring that vyaptis are free from all vitiating conditions is called upadhinirasa. One way of insuring this is by the repeated observation of both constituents of a relationship under all possible circumstances to make certain that the relationship is in fact invariable. Another way is to employ hypothetical critical argumentation or tarka. But nyaya places the greatest emphasis on samanya laksana -- the perception of classes -- as the major means for insuring the validity of vyaptis.

Classifications of inference. Nyaya provides three general classification systems for inference. The first classification system is based on psychological grounds; the second is based on the nature of vyapti or the universal relationship between the middle and major terms; and the third is based on the logical construction of the inference.

According to the first system of classification, there are two kinds of inference: svartha, meaning "for oneself," and parartha, meaning "for others." In svartha, the purpose of the inference is for one to gain correct knowledge by oneself and for himself. In this kind of inference, the whole process of reasoning is internal -- one employs systematic logical reasoning to protect oneself from confusion and doubt and to arrive at correct inferential knowledge. In parartha, on the other hand, the inference is meant for others. Here someone is trying to prove the truth of his view. For instance, a man who is convinced of the existence of fire on a hill would use parartha when attempting to convince others of the fire's existence.

The second classification system divides inferences into three categories: purvavat, sesavat, and samanyatodrsta. Both purvavat and sesavat inferences display causal uniformity between the middle and major terms, while samanyatodrsta inferences exhibit non-causal uniformity of the middle and major terms. Here the term cause refers to an invariable and unconditional antecedent of an effect, and effect refers to an invariable and unconditional consequence of a cause. When an unperceived effect is inferred from a perceived cause, that inference is deemed a purvavat inference. For example: "It will rain because there are dark heavy clouds in the sky, and whenever there are dark heavy clouds, it rains." Here the future rain (effect) is inferred from the appearance of dark heavy clouds (cause). Sesavat is the reverse type of reasoning, in which an unperceived cause is inferred from a perceived effect. For instance: "It has rained recently because there is a swift muddy current in the river, and whenever there is a swift muddy current in the river, it has recently rained." Here we infer the cause (the past rain) from the effect (the swift muddy current). And finally, in samanyatodrsta, the third type of inference in this system of classification, the invariable concomitance between the middle term and the major term does not depend on a causal uniformity. One term is not inferred from the other because they are uniformly related. In this kind of reasoning, conclusions are based on direct experience and on generally known truths. An example of this sort of inference is the movement of the moon which is inferred on the basis of its changing position in the sky, although the movement of the moon is not perceived directly by the senses.

The last general classification system is based on the nature of induction, by which one obtains the knowledge of the invariable concomitance between the middle and the major terms of an inference. This system distinguishes among three types of inference. In the first, kevalanvayi, the middle term is only positively related to the major term. For example: "All knowable objects are nameable." In the second, kevalavyatireka, the middle term is only negatively related to the major term. For example: "Whoever is dead has no pulse: this person has a pulse; therefore he is not dead." In the last category, anvayatireki, the middle term is both positively and negatively related to the major term. This is the joint method of both anvaya and vyatireka. For example: "All smoky objects are on fire: the hill is smoky; therefore, the hill is on fire. No nonfiery object is smoky; the hill is smoky; therefore the hill is on fire."

The fallacies of inference. In the nyaya system, fallacies of inference are called hetvabhasa. This term literally means "a reason (hetu) that appears to be valid but is not really so." There are five kinds of fallacies, called sabyabhicara, viruddha, satpratipaksa, asiddha, and badhita. The first, sabyabhicara, means "irregular middle." In a correct inference, the middle term is uniformly and without exception related to the major term. An irregular middle term is destructive to an inference because it can lead to a wrong conclusion. For example: "All Himalayan beings are saints; tigers are Himalayan beings; therefore, tigers are saints." The conclusion of this inference cannot be said to be correct, because the middle term, Himalayan beings, is not invariably related to the major term, saints. Himalayan beings come in many different varieties. Instead of leading to one single valid conclusion, such an irregular middle term leads to varied opposite conclusions.

Viruddha, the second kind of fallacy, means "contradictory middle." A contradictory middle is one that dismisses the very proposition it is meant to prove. For example: "Sound is eternal, because it is caused." Whatever has a cause is noneternal, and so here the middle term, caused, does not prove the eternity of sound but rather confirms its non eternity. The distinction between an irregular middle and a contradictory middle is that while the irregular middle fails to prove its conclusion, the contradictory middle proves the opposite of what is intended.

The third type, satpratipaksa, means "inferentially contradictory middle." This type of fallacy arises when the middle term of an inference is contradicted by the middle term of another inference that proves a completely opposite fact about the major term. For example, the argument "Sound is eternal because it is audible" is contradicted by the inference "Sound is noneternal because it is produced, as a pot is produced." The distinction between a contradictory middle and an inferentially contradictory middle is that in the former, the middle term itself proves the contradiction of its conclusion, while in the latter, the contradiction of the conclusion is proved by another inference.

The fourth type of fallacy is asiddha, an unproved middle. In this type of fallacy, the middle term is not an established fact but is an unproved assumption. For example: "The sky-lotus is fragrant because it has lotusness like a natural lotus." Here the middle term, lotusness, does not have any substantial existence because such a thing as a sky-lotus actually does not exist.

The fifth is badhita, a noninferentially contradicted middle. Here the middle term is contradicted by some other source of knowledge. Examples are: "Fire is cold because it is a substance," and "Sugar is sour because it produces acidity." Here "cold" and "sour" are the major terms and "substance" and "acidity" are the middle terms. The existence of heat in the fire and sweetness in sugar is directly perceived by the senses, so one has to consider substance and acidity as contradictory middle terms. Therefore, the inference is fallacious.


According to nyaya, comparison is the third valid source of experiential knowledge. This kind of knowledge comes when one perceives the similarity between the description of an unfamiliar object and its actual appearance before one's senses. For example, suppose that a trustworthy person has told you that there is such a thing as a crabapple that looks like a regular red apple but is smaller and has a longer stem. One day in the woods you come upon a tree bearing fruit that you have never seen before but that reminds you of apples. You then remember your friend's description of crabapples, and you come to the conclusion that this must be a crabapple tree.

This source of knowledge, upamana, is not recognized as valid in many of the other systems of Indian philosophy. The carvaka system of philosophy, for instance, does not accept this as a source of know]edge, because this system maintains that perception is the sole source of valid knowledge. The Buddhist system of philosophy recognizes upamana as a valid source of knowledge but regards it as a mere compound of perception and testimony. The vaisesika and sankhya systems explain upamana as simply a form of inference, and the Jain system maintains that it is merely a kind of recognition. The mimamsa and vedanta systems agree with nyaya in considering upamana as an independent source of knowledge, but they explain it in a different way, which will be discussed in the chapter on mimamsa.


Sabda or testimony literally means "words"; it is the knowledge of objects derived from words or sentences, and is, according to nyaya, the fourth and final source of valid experiential know- ledge. Not all verbal knowledge, however, is valid. In nyaya philosophy, sabda is defined as the statement of an apta, a person who speaks and acts the way he thinks. Such a person's mind, action, and speech are in perfect harmony, and he is therefore accepted as an authority. Thus his verbal or written statement is considered to be a valid source of knowledge. The Veda is considered to be the expression of certain venerable aptas, great sages who realized the truth within and who transmitted their experiences into words. The validity of the Veda is derived from the authority of these aptas.

The validity of verbal knowledge depends upon two conditions: first, the meaning of the statement must be perfectly understood, and, second, the statement must be the expression of a trustworthy person, that is, an apta. There are two main ways of classifying sabda, or testimony. The first method of classification divides testimonial knowledge into two categories based on the nature of the object of the knowledge. The first category consists of the trustworthy assertions of ordinary persons, saints, sages, and scriptures on matters related to the perceptible objects of the world. Examples are the evidence given by expert witnesses in court, the statements of reliable physicians about physiology, and scriptural declarations concerning the performance of certain rites. The second type of testimony consists of the trustworthy assertions of persons, saints, sages, and scriptures on matters concerning the supersensible realities. Examples are a physicist's assertions about atoms, a nutritionist's statements regarding vitamins, a prophet's instructions on virtue, and scriptural statements about God and immortality. The second way of classifying sabda is based on the nature of the source of the knowledge. This method categorizes all testimony as being either scriptural or secular. Here the word scriptural refers only to the sacred writings related to the Veda and to the Veda its]f. The words of scriptural testimony are considered to be perfect and infallible. Secular sabda is the testimony of fallible human beings and therefore may be either true or false; secular testimony that comes from a trustworthy person is valid, but the rest is not.

The nyaya system gives a detailed description of the nature of sabda because testimony is considered to be a valid source of knowledge and should therefore be analyzed thoroughly. In a scripture or a testimony, words and sentences are used -- but what is a sentence, what is a word, and what is the nature of their construction? Here, a sentence may be viewed as a group of words arranged in a certain manner, and a word as a group of letters or phonemes arranged in a specific order. The essential nature of any word lies in its meaning, and there must be specific rules governing the arrangement of words in the formation of sentences. Without such rules, the words spoken even by a trustworthy person -- an apta -- could be reordered to convey a different meaning from the one intended or could mislead a common person because of their lack of clarity of meaning.

The Potency of Words

The nyaya system states that all words are significant symbols and that all words have the capacity to designate their respective objects. This capacity of words is called shakti, potency, and in the nyaya system, potency is said to be the will of God. The words used in a sentence have certain meanings because of the potencies within them, and that is why they express certain meanings in a particular context. So the ordering of words in a sentence is very important. In addition, nyaya maintains that there are four other factors that are essential in the proper functioning of sentences, and without the fulfillment of these four conditions a sentence cannot express the intended meaning These conditions are: akamksa (expectancy), yogyata (fitness), sannidhi (proximity), and tatparya (intention).

Akamksa, the first condition, means "expectancy." Akamksa is the quality by which all the words of a sentence imply or expect one another; it is the need that each word has for the other words in that sentence. According to the nyaya system. a word is not in itself capable of conveying a complete meaning; it must be brought into relationship with other words in order to express the full meaning intended. For example, when someone hears the word "bring," he asks or he thinks about what to bring. It could be a jar, a book, a pencil, a doughnut, or anything else. Thus, expectancy is the interdependence of the words in a sentence for expressing a complete meaning.

Yogyata, the second condition, means "fitness." It refers to the appropriateness of the words in a sentence, to the absence of contradiction in its terms. For example, sentences like "Moisten with fire,", or "He is frustrated because of his inner peace," make no sense because there is a contradiction between fire and moistening, between frustration and peace. Fire has no ability to moisten anything, and inner peace cannot engender frustration. Therefore, although these sentences may be grammatically correct, they do not express valid knowledge.

Sannidhi, the third condition, means "proximity." It is very important for words to be used within the limits of an appropriate time and space. If the duration of their use is prolonged, then words no longer have the capacity to give the desired meaning. For example, if someone who desires to make a statement speaks one word today, another word tomorrow, and a third the day after, his efforts at effective communication are certain to fail. The same holds true for the written word. If someone writes one word on page one, another on page three, one more on page five, and another on page ten, then his meaning will not be communicated effectively. Continuity of time and space is therefore essential for a sentence to convey meaning.

Tatparya, the fourth condition, means "intention", and it refers to the meaning one intends a sentence to convey. A word may have various meanings depending on its context, so one has to be careful to determine the real intention of the person who uses the word. This is also the case with scriptural testimony -- even the greatest scholars have disagreements concerning some passages because they do not understand the original intention of those sentences. A very simple illustration is this: Suppose someone tells you to bring him a bat; you have no way of knowing whether you are being asked to provide a particular type of flying mammal or a wooden club. To understand the real intention of a sentence, one has to comprehend accurately the context in which the words are used. Because of the unique nature of the Sanskrit language and its symbolic usages, the Veda and related ancient religio-philosophical scriptures are full of this kind of complexity and indeterminability of intention. In order to clarify this and understand the Vedic testimony properly, nyaya recommends that one study the mimamsa philosophy because it provides systematized rules and interpretations for understanding the real meaning of the Veda.

The Nature of the Physical World

As mentioned previously, the nyaya system groups all the objects of the world into twelve major categories: soul, body, senses, objects of the senses, cognition (buddhi), mind (manas), activity, mental modifications, rebirth, feelings, suffering, and absolute freedom from all sufferings. Not all these objects of knowledge are found in the physical world because the physical world is composed only of the four gross elements -- earth, water, fire, and air. Although the soul and the mind are involved in the physical world, they are not physical elements. Likewise, time and space are completely nonmaterial, but they nonetheless belong to the physical world. Akasa (space or ether) is considered to be a physical substance, but it is not considered to be a productive cause of anything In fact, the ultimate constituents of earth, air, fire, and water are eternal and unchanging atoms. Ether and time and space are also eternal] and infinite substances, each being one single whole. All in all, the nyaya theory of the physical world is very similar to that of the vaisesika school, and a more detailed discussion of this world view will be provided in the next chapter.

The Concept of the Individual Soul

There are many apparently different concepts of the soul among the various schools of Indian philosophy. The carvaka system states that the soul consists of the living physical body and its attributes. According to Buddhist philosophy, there is no soul. Buddhism teaches that the stream of ever-changing thoughts and feelings is the ultimate reality. This may be termed soul, but it is not considered to be a permanent entity, as is maintained by other philosophies.

According to the concept of soul held by the nyaya and vaisesika systems, the soul is a unique substance, of which all desires, aversions, pleasures, pains, and cognition are qualities. There are different souls in different bodies. The soul is indestructible and eternal, and its attribute is consciousness. Because it is not limited by time and space, the soul is also seen as infinite or all-pervading. There are many souls, because one person's experiences do not overlap those of another person; one's, experience is completely distinct from any other's.

Nyaya gives numerous arguments to prove the existence of the soul. It first argues that the body is not the soul because immaterial consciousness cannot be said to be an attribute of the material body, which in itself is unconscious and unintelligent. Neither can the functioning of the senses explain the process of imagination, memory, and ideation -- none of these functions depends on any external sense. The mind can also not be the soul because the mind is considered to be an imperceptible substance. Nor can the soul, as the Buddhists maintain, be identified as the ever- changing series of cognition. The soul cannot be said to be an eternal and self-effulgent consciousness because consciousness cannot subsist without a certain locus. At the same time, the soul is not mere consciousness or knowledge but is the knower of knowledge and the enjoyed of objects. In sum, the soul is not consciousness but is a substance having consciousness as its attribute.

The soul experiences the external world through the mind and senses. All the cognition and conscious states arise in the soul when the soul is related to the mind, the mind to the senses, and the senses to external objects. It is because of this sequential contact or relationship that the whole process actuates; otherwise there would be no consciousness in the soul. In its disembodied or disintegrated state, the soul has no knowledge or consciousness. How then can one know whether there is such a thing as an individual soul? The nyaya system answers that the soul is not known by sensory perception but rather by inference or testimony. The existence of the soul is inferred from the functions of desire, aversion, and volition, from the sensations of pain and pleasure, and from memories of these. These memories cannot be explained unless one admits a permanent soul that has experienced pain and pleasure in relation to certain objects in the past. The process of knowledge based on memory requires to}e existence of a permanent self that desires to know something and then desires to attain certain knowledge about it. Desire, volition, pain, and pleasure cannot be explained by the body, senses, or mind. Just as the experiences of one person cannot be remembered by another person, the present states of the body or the senses or the mind cannot remember their past states. The phenomenon of memory must depend upon a permanent entity -- the soul. One's own soul can be known through mental perception, but someone else's soul in another body can only be inferred.

The Concept of Liberation

Like all the other systems of Indian philosophy, the nyaya system maintains that the ultimate goal of human life is to attain liberation. By liberation is meant absolute freedom from all pain and misery. This implies a state in which the soul is completely released from all bondage and from its connection with the body. It is impossible for the soul to attain the state of complete freedom from pain and misery unless the soul is totally disconnected from the body and senses. In liberation, the soul is unconditionally and absolutely freed from all shackles forever.

To attain the state of liberation, one has to acquire true knowledge of the soul and of all the objects of experience. This knowledge is called tattva-jnana, which means "to know reality as completely distinct from unreality." Nyaya philosophy prescribes a three-stage path for reaching the goal of liberating knowledge. The first step is sravana, the study of the scriptures. One has to study the spiritual scriptures and listen to authoritative persons and saints. Following this, one must use his own reasoning powers to ponder over what he has learned. This process of rumination is called manana. Finally, one must contemplate on the soul, confirm his knowledge, and practice that truth in his life. This is called nididhyasana. Through the practice of sravana, manana, and nididhyasana, a person realizes the true nature of the soul as being totally distinct from the body, mind, senses, and all other objects of the world. The truth realized within dispels the darkness of self-identification and misunderstanding (mithya-jnana) concerning "I-ness" and "Thy-ness." When this happens, a person ceases to be moved by his passions and impulses and begins to perform his duties selflessly without having any desire to reap the fruits of these actions. The fire of true knowledge roasts one's past karma like seeds, thereby making them unable to germinate. Thus, true knowledge leads a person to the state where there is no cycle of birth and death. This state is called liberation.

The Concept of God

According to nyaya, God is considered to be the operative cause of creation, maintenance, and destruction of the universe. God does not create the world out of nothing or out of himself but rather out of the eternal atoms of space, time, mind, and soul. The creation of the universe refers to the ordering of these eternal entities, which are in coexistence with God, into a mortal world. Thus God, as the first operative cause of the universal forces, is the creator of the world. And God is also the preserver, as he causes the atoms to hold together and continue their existence in a particular order that maintains the physical universe. God is also called the destroyer of the universe, because he lets loose the forces of destruction when the energies of the mortal world require it. God is one, infinite, and eternal, and the universe of space and time, of mind and soul, does not limit him. God is said to possess six perfections: infinite glory, absolute sovereignty, unqualified virtue, supreme beauty, perfect knowledge, and complete detachment.

Nyaya provides a few arguments to establish the theory of God. The first is the causal argument. According to this line of reasoning, the entire universe is formed by the combination of atoms. Mountains, fields, rivers, and so on must have a cause, for they are made up of parts, possess limited dimensions, and are not intelligent. This being so, they cannot be the cause of themselves; they require the guidance of an intelligent cause. That intelligent cause must have direct knowledge of all matter and of the atoms that underlie all matter. He must be omnipresent and omniscient. This intelligent entity cannot be the individual soul because the knowledge of the soul is limited -- a soul, for instance, does not have the knowledge of other souls. Therefore, there must he an ultimate intelligent entity, which is termed God.

The second argument is based on adrsta, which means "the unseen" or "the unknown," and may be translated as providence or fate. The philosophers of the nyaya system inquire as to why some people are happy and others are not, why some are wise and others ignorant. One cannot say that there is no cause, because every event has a cause. The causes of pain and pleasure must therefore be one's own actions in this life or in previous lives. People enjoy or suffer according to the merits or demerits produced by their past good or bad actions. This law of karma, which governs the life of every individual soul, requires that every human being must reap the fruits of his own actions.

There is often a long interval of time between an action and its effect, however, and many pleasures and sorrows cannot be traced to any action performed in this life. Likewise, many actions performed in this life do not produce fruits immediately. The subtle impressions of all one's actions persist long after the actions themselves and are collected in the soul in the form of credits or merits (punya) and deficiencies or demerits (papa). The sum total of all merits and demerits that are accrued from good or bad actions is called adrsta, fate, and this produces present pain and pleasure. Adrsta is not an intelligent principle, however, and it cannot inspire its own fructification. It must therefore be guided or directed by some intelligent agent to produce the proper consequences. The individual soul cannot be said to be the director or controller of adrsta because souls do not know anything about their adrsta. Thus, the almighty intelligent agent who guides or directs adrsta through the proper channels to produce the proper consequences is the eternal, omnipotent, and omnipresent supreme being termed God.

A third nyaya argument for the existence of God is based on scriptural testimony. According to this reasoning, the Vedas, Upanisads, and all other authoritative scriptures state the existence of God. These scriptures were not written by common people but were formulated by great sages who experienced truth from within. Thus, the authority of testimony depends on direct experience, which is the only source of knowledge about any and all facts. The fact of the existence of God is experienced directly by individual souls, and some of these individuals have expressed their God-realizations. The Veda expresses such direct experiences of God. Therefore, God exists.