Indian Logic: Means of Knowledge |Logical Reasoning | UGC NET Paper 1

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Indian Logic: Means of Knowledge UGC NET
Indian Logic: Means of Knowledge

Indian Logic

Indian Logic: Logic is the study of inference and argument. Logic has always fascinated humankind for its sheer scope of immense arguments and discussions. It is the scientific study of ‘reasoning. Using the term “Scientific” does not mean anything related to the basic sciences. The usage of the term is primarily more as an adjective meant to qualify how the study is undertaken. Indian logic has been differently viewed in the different ages. Many academicians have discussed Indian logic as a system by dissociating ‘Buddhist logic’ from it. Indian logic must be studied as the form of correct arguments and inference patterns, which was developed in India from the methodology of philosophical debate.

Schools of Indian Logic

The development of Indian logic over the ages can be classified into the following categories:

  • Ancient
  • Medieval
  • Modern
UNIT VI – Logical Reasoning (Click below on the topic to read the study notes)

Ancient Indian School (650 B.C. to 100 A.D)

Indian ancient school had a great impact on the development of Indian logic. Ancient school offers a fine treatment of soul distinguishing carefully between knowledge and work. The Upanishads are dealt with the soul and its destiny constituted a very important branch of study called Aatmaa-vidyaa (the science of soul), and Adhyatma-vidyaa (the Divine Science).

Aatmaa Vidya was at a later stage called Ānvīkṣikī (the science of inquiry). About 650 B.C. Ānvīkṣikī bifurcates into philosophy and Logic, named as Darsana and Hetu-Vidya or Tark-Vidyaa, respectively.

However, tark-vidya was not received with favor by the particular section of the Brahmanas. In the Ramayana, Valmiki discredits those who are indulged in the seriousness of the science of Logic. Vyasa in Mahabharata, says that who has the addiction to logic, will be turned into a jackal in his next birth. Several stories of inflicting of penalties on those given to the study of Tark- Vidyā are found in plenty in the Skandapurāna and other works.

Despite of it, Ānvīsikī was held in very high esteem due to the authority that it attaches to the vedas. Kings were trained in logic, and the entity of reasoning was acknowledged in the administration of justice.

Kautilya, in his arthaśāstra characterises Ānvīshikī (logic) as the lamp of all sciences. It seems that the unfavorable criticism to which Ānvīsikī had long been exposed, terminated practically in the first century A.D. under the name of Nyāya- Sāstra.

Between 1 A.D. and 100 A.D., there was the growth of the name Nyāya (‘right’ or ‘justice’). Nyaya-Sastra is, therefore, the science of right judgment or valid reasoning. It is the science of inference for the sake of others. It is also the science of demonstration.

The first regular work on the Nyāya Sāstra is the Nyāya Sūtra or “aphorism on true reasoning.” The book is divided into five other books, each book containing two chapters called āhnikas (diurnal portion). It contains the references to the Sānkhya, Vaiśesika, Yoga, Mimāṃsā, Vedānta and Buddhist System of philosophy. The Nyāya sūtra consists of sixteen categories, which comprise all the topics of the course debate.

The categories are:

  1. The right means of knowledge (pramāna)
  2. The object of right knowledge (prameya)
  3. Doubt (samśya)
  4. Purpose ( prayojana)
  5. Example (drastānta)
  6. Tenet (sidhānta)
  7. Members (avayava)
  8. Confutation (tarka)
  9. Ascertainment (nirnaya)
  10. Discussion (vāda)
  11. Wrangling (jalpa)
  12. Cavil (vitaṇḍā)
  13. Fallacy( hetrābhāsa)
  14. Quibble (chhala)
  15. Analogue (jāti)
  16. The point of defeat (nigrahasthāna)

Perception, inference, comparison, and a word or verbal testimony are the means of right knowledge. Soul, body, senses, intellect, mind, activity, fault, transmigration, fruit, pain, and emancipation are the objects of the right knowledge.

Medieval School of Indian Logic (100 A.D. to 1200 A.D.)

The unique features of medieval logic are the termination of the ancient school, the formation of school under the influence of Jain and Buddhist ideas of logic. The ancient logic dealt with sixteen categories comprising heterogeneous elements as a doctrine of salvation and the nature of soul etc. Inference, a kind of pramāna, which was briefly noticed in the ancient logic, receives full treatment in the medieval school. The number of technical terms were coined, and great subtleties were introduced in the definitions. The medieval logic thus formed, is called pramāna sāstra in Sanskrit, which means the science of the right knowledge.

According to the Jains, logic was called hetu. Hetu as similar with valid knowledge is stated to be of four kinds:

  1. Knowledge derived from perception (pratyaksa)
  2. Knowledge derived from inference (anumana)
  3. Knowledge derived from comparison (upamana)
  4. Knowledge derived from verbal testimony (sabda)

The main categories, in the course of study of logic according to the Jain school are:

  • Valid knowledge (pramāna): This is the knowledge which ascertains the nature of what was uncertain to one’s
  • Syllogism (Vyāpti): This is the inseparable connection between two
  • Reason (hetu): Reason is divided as (a) perceptible and (b) imperceptible.
  • Example (dṛṣṭānta): For the sake of explaining matters to men of small intellect,the example becomes a part of inference.
  • Inference (anumāna):
  • Verbal testimony (āgama): This the knowledge of object derived from the words of reliable persons or scriptures in virtue of their natural fitness or
  • Scope of valid knowledge (viṣaya)
  • Fallacy (ābhāsa)

The following categories are considered by the Buddhist school of logic:
Valid knowledge: only two pramānas, perception and inference in opposition to the four pramānas of the Nyāya-Sutra,
Reason (hetu): Similar concept of ‘hetu’ according to the ancient school.
Example (dṛṣṭānta): It is to pointing out the connection of the reason with the major terms, one should state examples.
Negation (apoha): An entity is defined as being the negation of its opposites.
Analogues (Jāti): The concept of analogues is almost similar to the concept of Jāti” in the Nyāya-Sutra.

Since the Brāhmaṇas did not differ in respect to their social practices from the Jains, as they did from the Buddhist. So, the Brāhmaṇas attack on Jain Logic was not as violent as that on the Buddhist Logic. In fact, the logical theories of the Jains are in many cases similar to those of the Brāhmanas. The different categories of logic as described in the Nyāya Sutra are very much similar to the Jain school but differ significantly from the Buddhist school.

Modern School of Indian Logic

In the Deccan regions of India, the decline of Buddhism commence in the seventh century A.D. The Brāhmaṇas, borrowed the Budhist logic from the work of the mediaeval school, but for other matters they went back to the works of the ancient school.

The works so composed in the modern period were technically called “Prakaraṇas” or Manuals of logic. The manuals are remarkable for their accuracy and lucidity.

The main categories of the cause of logic as identified in the manuals are:
 A. Pramāṇa (valid knowledge): which can be classified into:

  • Perception (pratyaksha)
  • Inference (anumāna)
  • Verbal Testimony (āgama)

B. Hetvābhasa (fallacy of reason): Which can be classified as-

  • Unproved (asiddha)
  • The contradictory (viruddha)
  • The uncertain (anaikāntika)
  • Non-tried or non-conclusion
  • Mistimed or incompatible reason
  • Non- erroneous contradiction

C. Example (udāharaṇa)
D. Verbal Testimony(āgama)
E. Emancipation (Mokṣha)

The modern school of Logic suggests that the soul is of two kinds, viz. the individual soul (aparaātma) and the supreme soul (para ātma). With the knowledge of the supreme soul, the individual soul attains final emancipation.


The tarka” is an important component of Logic. But it does not provide any originality in information. It only proves what has already been known by regular syllogism. The sānkhya, Yoga and Vedānta believe in buddhi but the Nyāya and the Vaiśesika do not consider Budhhi as reason. It is only an adventitious consciousness that arises like a spark or light when mind (manas) comes into contact with the aatman.

We have tried to compile the effort to trace the history of development of logic in India. In India, Logic came under the scrutiny of intellectuals as early as 650 B.C. and surviving a span of more than 2600 years. The system of logic in India in the modern form is an assimilation of various schools of logic. The thoughts of the schools of Logic deeply influence the Indian society.

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