Texts of Indian Philosophy
Dharmarāja Adhvarīndra, in his text Vedānta Paribhāșā, defines valid knowledge to be that knowledge which has for its object something that is not already known and is not contradicted and if it is already known then it should not be contradicted. The first chapter of the text titled Perception begins with an objection on the contradiction of the unreal nature of the jar and its knowledge being valid. The objection is answered by saying that they are not contradictory in the transitory state but only after the realisation of Brahman, a jar etc, are contradicted. At the same time he states six means of valid knowledge, perception, inference, comparison, verbal testimony, presumption and non apprehension respectively. He accepts perception as a valid means of knowledge and at the same time says that the jar becomes unreal as one realises Brahman. He uses the example of shell in the silver to explain it. One sees shell from a distance to be silver and says ‘this is silver’ which is a single piece of knowledge. This might be the case that the perception of shell has led to the memory of silver perceived in the past. But this has not to the combination of the perception of ‘this shell’ and the memory of ‘that silver’ that are two different cognitions. It is a case of undiscrimination between the perceiving ‘this shell’ and remembering ‘that silver’. Thus, he concludes by asserting the possibility of error in perception. He uses this analogy to explain the nature of the phenomenal world as unreal and Brahman as the ultimate reality.
Unlike Vedānta, Mimaṃsā school holds the belief that all immediate kinds of knowledge are true. On the illusion of rope as a snake they say that it is just a case of non discrimination between the two pieces of knowledge i.e. perception and memory. They call this phenomenon as akhyātivāda. Within Mimaṃsā School, the two prominent thinkers Prabhākara and Kumārilabhatt understand this case differently.
Prabhākara understands knowledge to be self luminous (svaprakāśaka) which manifests itself and does not require anything else for its manifestation. So he does not admit illusion as an error in the logical sense but calls it imperfect knowledge or partial truth. It is non apprehension of the distinction of two different pieces of knowledge and their objects. This error is of omission and not commission. Thus he calls it vivekakhyāti or bhedāgraha or saṃsāragraha.
Unlike Prabhākara, Kumārilabhatt understands the error as misapprehension than non apprehension. He says that this error is not just of omission but also of commission as error, according to him, is a single psychosis than two different pieces of knowledge that are imperfect in nature. The two cognitions appear to be united which is partial misrepresentation. He calls it viparītakhyāti or saṃsārgagraha.
Nyāya – Vaiśeșika being the realist school of the Indian philosophy attempts to explain