As Shankara seeks to interpret our world phenomenon within the meaning of the theory of illusory perceptions, he considers very carefully the aspect of errors in perception, all the more, an explanation for these errors, presented by other Indian philosophy schools, which makes the creed of Advaita unconvincing. The followers of Mimamsa completely ignore the likelihood of errors in perception, arguing that all consciousness is truthful. If Mimamsa`s theory was correct, the position of Advaita would have been completely unfounded. The followers of the Advaita were therefore ought to study this theory. In fact, Mimamsa`s school adherents advocate that what is known as illusion (for example, the case with the snake and the rope), actually, is not a single, plain type of knowledge, but a combination of memory and comprehension. Shankara`s followers insist on the following main points, while refuting Mimamsa`s explanation. The judgment that expresses the false viewpoint "this is a snake", points to the case that there is only one kind of knowledge. It is possible that the apprehension of the existent subject ("this") really conjures a reminiscence of the snake, construed precedently, notwithstanding if this perception is not combined with the memory, in order to form a single state of understanding.
The Mimamsa`s theory of reliability consists in: a) the reliability of knowledge arises from the very conditions that give rise to this knowledge, and not from any supernatural circumstances; b) the reliability of knowledge is obvious, since knowledge has already emerged; c) certainty does not require the verification of the known through some other kind of knowledge, for example, by inference. According to this view, truth is self-evident. Whenever any knowledge arises, it brings confidence in its own truth. Sometimes another kind of knowledge may indicate that this certain belief is wrong, or that the conditions of knowledge do not conduce to learn correct knowledge. In this case, among few unfavourable conditions, can be drawn a conclusion that such knowledge is false. Thus, the falsity of knowledge is set by the output, while the truth is self-evident.
In its turn, the school of Nyaya-Vaisesika, tries to explain the misperceptions in a practical mode. Pointing to the fact that a misperception is only special (uncommon) example of perception, which remained in the memory image (for example, the image of a snake), conceived in the past, is so vividly recalled (by the perception of similarity of the rope and the snake) that the image, conceived in the memory is equivalent to direct contemplation. Therefore, what really existed in the past (for example, a snake that was seen earlier and elsewhere) appears to us now through a revived image. Thus, according to the followers of Advaita, the illusion gives no possibility to perceive a thing that never existed. None unreal object was ever perceived. Therefore, this view of the world cannot be considered a falsehood without the presumption of the true-life world, for example, in the past; the absolute unreality of the world cannot be proved.
The followers of Advaita`s theory reject this viewpoint in the following main reasons: the perception of an object in a given place and at a given time, which exists in some other place and at other time, is nonsensical.
The position of a relatively stable structure of the external world is not removed by Shankara from his description of reality. He does not think that the perception of a chair or a table is the perception of a certain ideal fact, because it would be to challenge any obviousness and to dissolve the material universe in an immaterial dream. Shankara taught that people have to recognize the existence of objects outside of their consciousness, because no one will cognize a column or a wall as simple forms of knowledge, but everyone is familiar with the column and the wall as objects of knowledge. One can determine from the fact that those who deny external objects, confirm this particular statement, by saying that a shape, perceived internally, looks as if it is something external. Besides, Shankara states that knowledge and object are different. The criterion of truth, concerning things is their correspondenc to the nature of things. Shankara admits that truth and falsehood belong to the object, but in the end there is only one reality - the Brahman, which no idea corresponds to, and in relation to which, all our judgments are imperfect. The world in the philosophy of Shankara is a visibility that is based on our ignorance.
Strictly speaking, the theory of truth of Shankara is radical empiricism. Logical truth is independent from psychological processes. While objecting the mimamsakas, Shankara argues that, although the search for the ideal of truth, or the process of psychological evaluation depend on the the individual`s free choice, the object of evaluation does not depend from all aforesaid. People can actively search for the truth or not – they are given the choice, but if they made a choice, and got down to business, the nature of truth can depend only on us. Cognition is never created or produced, it always manifests itself or openes. Although such manifestation may be a temporary process, but what appears, does not depend on time. Cognition has no history, whereas the life of the mind has one. Perception and conclusion are means of expression and contagion of knowledge in the constraints imposed by the empirical life.