The first "category" is the means of acquiring knowledge, and it is important, because it makes for disappearance of doubt; and when doubt disappears, we can understand the properties of things. We cannot say that there are no proper means of acquiring knowledge; and they are really four in number, sense perception, inference, analogy, and oral evidence or the testimony of the trustworthy and the wise; and it is necessary to understand their character and scope.
Doubt: Doubt disappears when we understand similar as well dissimilar properties of things. It disappears as a result of mental effort; but it is a mental effort itself, and so long as it continues, the mental effort continues too.
The means of acquiring knowledge: It is sometimes said that there are no proper means of acquiring knowledge, because they cannot be valid for all time. But we have to make the best use of all the means we have; and the fact that we cannot have any that are valid for all time does not mean that we can deny their validity altogether. But it is even possible to show that certain things are true for all time. For instance, if it is proved that there is sound, it is also proved that there is an instrument that produces it; and that is true for all time. What is, however, required is that there should be a balance between a thing to be proved and its evidence.
Sense-perception: There can be no sense-perception if the soul and the mind do not participate in it. As knowledge is a characteristic of the soul, it participates in sense-perception, which is a form of knowledge; and the mind participates in it too, because it is its characteristic to prevent simultaneousness of perception.
It is because of sense-perception that the connection between a sense-organ and its object is expressed by means of the same word.
Inference: Sense-perception has its own limitations, and cannot take, us very far; whereas we wish to have perfect knowledge, the knowledge of the whole. Indeed, if there were no proof regarding the whole, we shall find that it is not possible to understand anything properly; and that is so because the mind is always attracted to the idea of the whole and dwells on it; and so it makes use of inference to understand things.
There are some who maintain that there is no such thing as present time. But were there no present time, we should be unable to grasp anything, not even the past and the future.
Analogy: There are some who believe that analogy is not a conclusive means of acquiring knowledge. But analogy, by its very definition, consists in the demonstration of what is not perceptible by means of what is perceptible; and so it would be of no value if the comparison were indistinct. Indeed, its special value consists in enabling us to sum up the whole idea, and to say that it is so and so in specific and not general terms.
Oral authority or testimony of the trustworthy: There are some who believe that oral authority or testimony of the trustworthy is a kind of inference, because the object itself is not perceptible and has to be inferred. Indeed, so far as their practical application is concerned, the two are not different; but the value of oral testimony consists in the fact that, because the information is conveyed by a trustworthy person, there is a firm conviction in regard to its import. There are certain things, like satisfaction, a burning heart and a splitting head, which cannot be perceived; and in such cases the testimony of a trustworthy person is our only means of acquiring knowledge. But there are some who believe that it is unworthy of being regarded as a means of acquiring knowledge because it is susceptible to a number of faults, falsehood, inconsistency of statement, and repetition. But this is not a valid objection, for these defects arise not from the nature of the means, but from the defect of the act, the actor, and the manner of producing a result. Its real defect, however, arises from a difference of time when a statement is made, as also from translation, for they may alter the whole idea. The Vedic hymns and the science of medicine are authoritative, but their authority is derived from the statements of trustworthy persons.
Some more problems of knowledge: There are some who believe that there are four other means of acquiring knowledge, traditional instruction, and inference from circumstances, equivalence, and proof from non-existence. But these are really included in the original four. In this connection it is necessary to have a proper idea of certain things: existence and non-existence; essential and secondary attributes; perception and non-perception, including the atom; identity and difference; and existence and eternity. The use of language is important too, specially with reference to the language of the Vedas, and it is necessary to understand their method of interpretation.
Other means of acquiring knowledge: There are some who believe that, in addition to these four, there are four other means of acquiring knowledge, traditional instruction, and inference from circumstances, equivalence, and proof from non-existence. But all these are really included in the original four.
The idea of existence and non-existence: When we describe a thing as non-existent, it does not mean that it is devoid of everything, including non-existence. For instance, before a thing is born, it appears to be non-existent; but it is only in a metaphorical sense that we say that such a thing is non-existent. So long as the fundamental notion of a thing remains, we cannot say that it is non-existent; but we can speak of even eternal things as non-eternal in a metaphorical sense.
The idea of essential and secondary attributes: There is no contradiction between the essential and secondary attributes of a thing.
The idea of perception and non-perception: Before we have spoken, a thing may be said to be unperceived; and the same effect is produced by means of covering or concealing; and so not speaking is like concealment so far as perception is concerned. But as non-perception is characterized by non-perceptibility, we cannot find its cause, for what cannot be perceived is intangible. It is, however, not co1rect to say that all intangible things are imperceptible.
The atom: We know that the atom, which is intangible, exists and is eternal. It may be argued that since it is imperceptible, we cannot know what lies within it. But we know that something does, for we are taught about it; only we may not be able to know what exactly lies within it, for a further study may lead to something else.
Identity and difference: The idea of difference arises from things that are different, and of identity from things that are identical. But there can be no real identity, because no two things are exactly alike.
Existence and eternity: A thing is said to be eternal when we cannot perceive the cause of its destruction. But if a thing is perceivable, but is not perceived, it would be an invalid argument to say that it does not exist. But if we are unable to perceive the cause of the destruction of an object, and our inability to do so persists, we may conclude that it is permanent.
The use of language, the language of the sacred books and their method of interpretation: We find that there are separate parts of a word or a compound; and we are taught to make a change, and substitute one part for another, which may raise a doubt as to its exact idea. But if a word expressed the idea of an object exactly according to the requirements of each case, there would be no reason for changing its form. But when we find that the whole idea of the text has become unbalanced, and we are filled with a doubt as to its exact meaning, it implies that it is necessary to make a change. For instance, when we find that there is an improper statement about a good man, we have the option to change the form of a word to understand its meaning. But this is not the only test; and a change of form may become necessary if we find that there is a conflict with the idea of Dharma; for when the form of words is changed, the objects described are found to conform to Dharma, and we do not find any transgression. There are, however, certain words like gold etc., the form of which does not require any change, because they are not connected with any transgression. There is a principle underlying this method of changing the form of words in order to understand their meaning: words expressing the idea of permanence do not require any change; those expressive of impermanence do. In certain cases, however, the form of words expressing even the idea of permanence may also be changed, if the objects described are beyond the grasp of the senses, and there is a doubt about their character as permanent. But in all cases where a state of transience is described, it is necessary to change the form of words. The reason for this change of form is that there is no restriction in respect of what may be described in the sacred books, and this absence of restriction is expressed in terms of absence of restriction in the use of words.
The change of form of a word, as the Mimansa has explained at considerable length, means its division into parts, letters or syllables or both, as may be necessary. The Mimansa tells us that if we deal with the text of the Vedas in this manner, their hymns of praise would be transformed into laws of Nature; and, as this method applies to the smrti too, it would transform "stories" into systems of philosophy.
There are certain cases where the form of words must necessarily be changed; and such are expressions relating to unexpected characteristics, misfortune, destruction, deterioration, excess, diminution, ambiguity, or some secret matter; and this change becomes necessary because the idea or object deviates from a natural or normal state. A word is made up of two things, basic form and terminations; and we have to divide it into parts because the common meaning of words in their juxtaposition in the text gives rise to a doubt as to whether the outward form, the Constituent parts, and the real nature of a thing have been properly described.