In the Indian philosophical tradition attempts have been made to reach at the right knowledge by the application of proper method of knowing.
All the schools of Indian philosophy except the Carvak accept anumana (inference) as a logical way of arriving at the right knowledge.
The Nyaya system is known as the pramana sastra that helps in obtaining right knowledge (prama). In Nyaya system we find there is extensive study about reasoning (tarka). In this system four independent methods of knowing are accepted. Inference (anumana) is one of them.
Similarly in Buddhistic system inference is accepted as a source of right knowledge. For them inferences involve arguments. Vedantins too have shown inference as a method of reaching at valid conclusions. Thus most of the systems of Indian Philosophy accept inference as a source of knowledge. In this chapter
Nyaya method of inference will be discussed in brief.
The study of inference includes the study of the form of the arguments and the basis of reaching at the conclusion. The form of the argument is understood as the step through which the conclusion is reached. For example, Naiyayikas accept five steps to reach at the conclusion.
So their form of the argument consists of five steps. Regarding the basis of reaching the conclusion, vyapti is accepted as the basis. Thus it is necessary to know what are the steps involved in reaching the conclusion and on what ground vyapti is accepted as the basis of the inference.
Form of the argument in the nyaya school of thought:
The Nyaya argument is pancavayavi in the sense that it has five steps. Those are namely, pratijna, hetu, udaharana, upanaya and nigamana.
Example of an argument:
1. Pratijna – The hill has fire.
2. Hetu – Because it has smoke
3. Udaharana – Whatever has smoke has fire.
4. Upanaya – This hill has smoke which is invariably associated with fire.
5. Nigamana – Therefore, this hill has fire.
Here the presence of the fire has been inferred from the presence of the smoke through five steps. The steps involved are in this following order.
a) What is to be proved?
b) The reason for what is to be proved.
d) Application of universal concomitance of present case.
e) The conclusion.
The features of this argument:
I) The last three steps have similarity with Aristotelian pattern of syllogism. It is in the form of AAA (Barbara) of the 1st figure.
ii) It has three terms very much like the classical syllogism. They are, Sadhya (corresponds to the major term), Paksa (corresponds to the minor team) and Hetu or Linga (corresponds to the middle term).
iii) The fourth step synthesizes all the three terms together. This synthesis is called linga paramarsa. The relation between paksa and sadhya (the two extreme terms) is decided on the basis of their relation with the middle tem hetu.
iv) The basis of drawing the conclusion is the relation of vyapti which is expressed in the third step. It is the nerve of inference. Vyapti expresses the relation of universal concomitance between sadhya and hetu.
v) Some logicians consider the first three steps to be in the form of an induction, specially of scientific induction type. In this sense, in the Nyaya form of argument both the inductive and deductive patterns are said to be blended together. But it is a case of reaching a particular premise through a general statement, (particular to particular through general, neither from general to particular nor from particular to general)
Even though some hold the view that Nyaya form of argument is both inductive and deductive by nature, the correct view seems to be that Nyaya argument is exclusively inductive like that of the case of scientific induction.