The doctrine of the self-validity of knowledge (_svata@h-prama@nya_) forms the cornerstone on which the whole structure of the Mima@msa philosophy is based. Validity means the certitude of truth. The Mima@msa philosophy asserts that all knowledge excepting the action of remembering (_sm@rti_) or memory is valid in itself, for it itself certifies its own truth, and neither depends on any other extraneous condition nor on any other knowledge for its validity. But Nyaya holds that this self-validity of knowledge is a question which requires an explanation. It is true that under certain conditions a piece of knowledge is produced in us, but what is meant by saying that this knowledge is a proof of its own truth? When we perceive anything as blue, it is the direct result of visual contact, and this visual contact cannot certify that the knowledge generated is true, as the visual contact is not in any touch with the knowledgeit has conditioned. Moreover, knowledge is a mental affair and how can it certify the objective truth of its representation? In other words, how can my perception "a blue thing" guarantee that what is subjectively perceived as blue is really so objectively as well? After my perception of anything as blue we do not have any such perception that what I have perceived as blue is really so. So this so-called self-validity of knowledge cannot be testified or justified by any perception. We can only be certain that knowledge has been produced by the perceptual act, but there is nothing in this knowledge or its revelation of its object from which we can infer that the perception is also objectively valid or true. If the production of any knowledge should certify its validity then there would be no invalidity, no illusory knowledge, and following our perception of even a mirage we should never come to grief. But we are disappointed often in our perceptions, and this proves that when we practically follow the directions of our perception we are undecided as to its validity, which can only be ascertained by the correspondence of the perception with what we find later on in practical experience. Again, every piece of knowledge is the result of certain causal collocations, and as such depends upon them for its production, and hence cannot be said to rise without depending on anything else. It is meaningless to speak of the validity of knowledge, for validity always refers to objective realization of our desires and attempts proceeding in accordance with our knowledge. People only declare their knowledge invalid when proceeding practically in accordance with it they are disappointed. The perception of a mirage is called invalid when proceeding in accordance with our perception we do not find anything that can serve the purposes of water (e.g. drinking, bathing). The validity or truth of knowledge is thus the attainment by practical experience of the object and the fulfilment of all our purposes from it (_arthakriyajnana_ or _phalajnana_) just as perception or knowledge represented them to the perceiver. There is thus no self-validity of knowledge (_svata@h-prama@nya_), but validity is ascertained by _sa@mvada_ or agreement with the objective facts of experience [Footnote ref 534].
It is easy to see that this Nyaya objection is based on the supposition that knowledge is generated by certain objective collocations of conditions, and that knowledge so produced canonly be tested by its agreement with objective facts. But this theory of knowledge is merely an hypothesis; for it can never be experienced that knowledge is the product of any collocations; we have a perception and immediately we become aware of certain objective things; knowledge reveals to us the facts of the objective world and this is experienced by us always. But that the objective world generates knowledge in us is only an hypothesis which can hardly be demonstrated by experience. It is the supreme prerogative of knowledge that it reveals all other things. It is not a phenomenon like any other phenomenon of the world. When we say that knowledge has been produced in us by the external collocations, we just take a perverse point of view which is unwarranted by experience; knowledge only photographs the objective phenomena for us; but there is nothing to show that knowledge has been generated by these phenomena. This is only a theory which applies the ordinary conceptions of causation to knowledge and this is evidently unwarrantable. Knowledge is not like any other phenomena for it stands above them and interprets or illumines them all. There can be no validity in things, for truth applies to knowledge and knowledge alone. What we call agreement with facts by practical experience is but the agreement of previous knowledge with later knowledge; for objective facts never come to us directly, they are always taken on the evidence of knowledge, and they have no other certainty than what is bestowed on them by knowledge. There arise indeed different kinds of knowledge revealing different things, but these latter do not on that account generate the former, for this is never experienced; we are never aware of any objective fact before it is revealed by knowledge. Why knowledge makes different kinds of revelations is indeed more than we can say, for experience only shows that knowledge reveals objective facts and not why it does so. The rise of knowledge is never perceived by us to be dependent on any objective fact, for all objective facts are dependent on it for its revelation or illumination. This is what is said to be the self-validity (_svata@h-prama@ya_) of knowledge in its production (_utpatti_). As soon as knowledge is produced, objects are revealed to us; there is no intermediate link between the rise of knowledge and the revelation of objects on which knowledge depends for producing its action of revealing or illuminating them. Thus knowledge is not only independent of anything else in its own rise but in its own action as well (_svakaryakara@ne svata@h prama@nya@m jnanasya_). Whenever there is any knowledge it carries with it the impression that it is certain and valid, and we are naturally thus prompted to work (_prav@rtti_} according to its direction. There is no indecision in our mind at the time of the rise of knowledge as to the correctness of knowledge; but just as knowledge rises, it carries with it the certainty of its revelation, presence, or action. But in cases of illusory perception other perceptions or cognitions dawn which carry with them the notion that our original knowledge was not valid. Thus though the invalidity of any knowledge may appear to us by later experience, and in accordance with which we reject our former knowledge, yet when the knowledge first revealed itself to us it carried with it the conviction of certainty which goaded us on to work according to its indication. Whenever a man works according to his knowledge, he does so with the conviction that his knowledge is valid, and not in a passive or uncertain temper of mind. This is what Mima@msa means when it says that the validity of knowledge appears immediately with its rise, though its invalidity may be derived from later experience or some other data (_jnanasya pra@ma@nyam svata@h aprama@nya@m parata@h_). Knowledge attained is proved invalid when later on a contradictory experience (_badhakajnana_) comes in or when our organs etc. are known to be faulty and defective (_kara@nado@sajnana). It is from these that knowledge appearing as valid is invalidated; when we take all necessary care to look for these and yet find them not, we must think that they do not exist. Thus the validity of knowledge certified at the moment of its production need not be doubted unnecessarily when even after enquiry we do not find any defect in sense or any contradiction in later experience. All knowledge except memory is thus regarded as valid independently by itself as a general rule, unless it is invalidated later on. Memory is excluded because the phenomenon of memory depends upon a previous experience, and its existing latent impressions, and cannot thus be regarded as arising independently by itself.