Most discussion of error in Indian philosophy centres on the possibility and the nature and explanation of perceptual error . There is little difficult in accounting for error that arises from use of unsound forms of reasoning or from misuse of sound forms. Perceptual error is more problematic. The Nyaya account of perceptual error is that error consists in perceiving something as other than it is. Error is always subjective.
Indian philosophers use standard examples to make their positions clear.
One standard example of perceptual error is the rope-snake. Nyaya philosophers see memory is a source of knowledge, it is the perception of traces of past experience has left on the mind. The traces are not perceived by the five external senses, but presumably by manas , the mind, acting as an internal sense. Memory plays a subsidiary but important role in perception. It qualifies the way I perceive something.