On The Nyaya Theory of Perception

The Nyaya theory holds that there are four distinct and independent methods or sources of knowledge — perception, inference, comparison, and testimony. All the four methods of knowing are of equal importance in respect of their value and importance, but perception (pratyaksa) can be seen as coming first and being the most fundamental because the other three methods of knowing must also make use of perception at some level.

Satischandra Chatterjee, in his book The Nyaya Theory of Knowledge, offers the following perspective on the Nyaya view of the critical role that perception plays in inference, comparison, and testimony (Page 129):

"For the Nyaya, however, perception is the basis on which we have a knowledge of other truths by inference as well as by comparison and testimony. Inference as a method of knowledge depends on perception. The first step in inference is the observation of a mark or the middle term (lingadarsana), and the observation of the relation between the middle and the major term. Hence, inference is defined as that knowledge which must be preceded by perception (tatpurvakam). Similarly, upamana or comparison as a method of naming depends on perception of the points of similarity between two objects. So also sabda or testimony is dependent on perception inasmuch as the first step in it is the visual or auditory perception of written or spoken words, and such words must come from a person who has a direct or intuitive knowledge of the truths communicated by him. So we see that perceptual knowledge is the ultimate ground of all other knowledge by inference, comparison and testimony."

In other words, perception is the final test of all knowledge—it is a direct source of knowledge, and the other three methods of knowing also presuppose perception.