The nature of the instrument used conditions the result of the investigation. The more sensitive and accurate the instrument, the more accurate is the observation, and, thus, the result. This is a well-known scientific fact. The world appears to be something to the naked eye, but it seems entirely different with the use of a microscope. The scientist seems to be approaching the truth of the object of his observation with the help of instruments. But the object, somehow, recedes further from his ken. There remains a chasm between the knower and the known. There is a gulf of difference between the subject and the object, between consciousness and matter. Consciousness cannot know matter; mind cannot know any object; the scientist cannot know anything. The scientist has to fail in the end on account of the very method and apparatus that he employs to investigate the nature of things.

One is likely to think that knowing the self is a simple matter. Everyone knows one's own self. Man refers to his own self by his name, by his designation, by his characteristics, by height, weight, width, and social relations. But this is a description of certain phenomena rather than the essentiality. Man, as a part of Nature, forms a content of space and time. Thus, his usual notion of his own self as a human being, as a man or a woman, as a relative of So-and-so, with such physical dimensions, etc., would be to know the self as he knows any other object in the world. Man, when he appears to himself as a physical body, is an object rather than a subject. Nobody looks upon himself as a subject, but sees himself as an object, as he sees a brick or a tree outside, because everyone can 'see' oneself and not just 'be' a pure subject. Everyone can see his body as he can see a building 'outside' 'in space'. So, from the point of view of mere observation through the sense organs, one's own self does not differ much from other objects of sense. The human body is as much an object of the senses as any other object. Thus, to say, "I am So-and-so" in a sociological or a merely physical sense would not be a correct definition of one's personality. When it was said that one has to know one's own self, it was not meant that one has to know it through the sense organs. The knowledge obtained through the senses, gathered through perception, is limited to the structure of the sense organs. If the organs were to be constituted in a different way, the picture that they would present would be quite a different thing altogether.

If the knowledge gained through the light rays impinging on the eyeballs is to be believed, it would be really a precarious knowledge indeed. The eyeballs are like lenses, and whatever be the nature of the lens that is used, to that extent the observation is conditioned. Man has been made in one way. He has got human eyes, and therefore he sees everything as human. Every human being has a similar set of eyes. But, if he had x-ray eyes, he would see a different world altogether. If it can be imagined that the eyes are made like microscopes, would anyone be able to live in this world? And yet, can anyone say that it would be a wrong perception? Perhaps, that would be a better and more reliable information. But the better perception would make one's life itself impossible as it is lived. In a way, it appears that ignorance keeps one happy. It is evident that it would be futile to depend upon the sense organs to supply correct knowledge. The sense organs include not merely the eyes, but also the ears, the sense of touch, the sense of taste, etc. None of these can be relied upon totally, because they are conditioned. Nothing can be known by examining the objects through the relative activities of the senses which change according to the spatio-temporal structure within which they function.

Space and time are supposed to be one complex whole. They are proved to be not two different things in the end. The objects, including human bodies, being placed in the context of space-time, are conditioned by the nature of the space-time complex. If man were to be living in a different order of space-time, he would certainly not be a human being as he is now.

But, man is a greater mystery and secret than can be observed on the outer surface. The analysis that Indian philosophers have made here is astounding. The study of philosophy in India began by a study of the nature of man. However, philosophy in the West, in its empirical meanderings, was confined to the study of the human individual as a subject from the point of view of experiences available in the waking life. Everyone, in the waking condition, is aware of the presence of the world outside, through the operation of the sense organs. What does man learn when he is awake? He sees a world. But how does he see a world? He is aware of the existence of the world by means of various factors that work together in bringing about this knowledge. Space and time are the primary factors. If space and time were not to be there to distinguish objects from one another, it would not be known that things exist at all. The conditioning influence of space and time is such that nothing can be known except as being present in space and time. Even if one closes the eyes and imagines the existence of an object, it would be a presence conceived in space and in time. Even if one tries to abolish the notion of space and time in imagination, one would be doing this act of abolishing the concept of space and time by being in space and time only. One cannot go out of this circle. It means that the mind is involved in the notion of space and time. All objects are spatio-temporal, including one's own self as an observed subject. Inasmuch as the mind is conditioned in this manner, one cannot hope to have an unconditioned knowledge of anything. The instruments of perception are restricted by the operation of space and time.

Not merely that; man is limited in many other ways. One's own reason itself is a limited faculty. There are certain mathematical and set ways of thinking which go by the name of logical affirmations. Logic is an instrument that the mind has manufactured out of the mathematical compulsion inflicted upon it by the operation of space and time. Two and two have to make four, and no one can think this in any other way. But one cannot rationally explain as to why two and two should make four. It has to be taken for granted that it must be like that, and no question can be raised about it. This is to give an example of how the mind functions peremptorily. It is such a type of conditioning that any question about it cannot be raised by the mind. The mind will regard any further question in regard to mathematical laws as absurd. The three angles of a triangle have to make two right angles; they cannot make more or less. Arithmetic, algebra, and geometry are fixed sciences. They are born out of certain intuitions cast in the mould of the operation of space and time in a given manner. Therefore, no one can gain insight into the nature of space-time or of the world which is conditioned by space and time. The logical approach, whether inductive or deductive, assumes certain premises which are incapable of logical demonstration. It does not carry one very far. An able and reliable guide in the world of space-time that it certainly is, it cries a halt and says, "Thus far, and no further."

There is something in man which rises above the limitations of mathematics and logic. One knows one's own self in a way that cannot be explained in terms of logic. Everyone knows that he exists. The fact, "I exist," need not be known by seeing with the eyes. Even if the eyes are closed, the ears are plugged, and the other natural senses do not operate, one can know that one exists. How does one know that he exists? This knowledge arises not by logic, nor by mathematics. It is not by a philosophical calculation that man comes to know that he is. The "I exist", or "I am", seems to be the only indubitable knowledge that can finally survive all tests and conclusions. The only infallible knowledge announces itself as the knowledge of the self, and every other knowledge is liable to further amendation, as, for example, in the advancement of the methods of science. Nature has been defined in hundreds of ways by scientific observations. What today is an infallible truth for science becomes tomorrow an outgrown, outmoded knowledge, to be supplanted by another observation altogether. Science goes on repeating its experiments and discovering newer and newer phenomena. What was truth yesterday is not necessarily so today. Science has not yet come to a conclusion as to what the ultimate truth is.

These questions relating to the nature of externally observed truths do not arise in regard to one's own self, because there is a faculty within man which cannot be identified with mental operation, or rational study, or sense activity. "I know that I am," is a revelation rather than a logical deduction. Intuitively one knows that one exists. Man's knowledge of his own self is indisputable, inviolable, and certainly true, and no one doubts one's own existence.

The great philosopher of India, Acharya Sankara, and another reputed philosopher of the West, Rene Descartes, thought on equal terms at different times in regard to the nature of the self. The doubting of the existence of one's own self has been regarded as impossible, because scepticism, while it can be applied to the nature of things outside, cannot be applied to the conclusions arrived at by the sceptic himself. The doubting of everything is an acceptance of the doubtless position which the sceptic maintains. The conclusions of a sceptical argument are not subject to the very same scepticism to which other things are subject. "I cannot doubt that I am doubting." This is the basic conclusion one finally lands upon. One can doubt everything but cannot doubt that one is doubting, because if one doubts the doubting, such doubting would have no sense. There is some peculiarity in man which defies the grasp at ordinary logical analysis. And this was the stand taken finally by most of the Indian philosophers. This mystery, this secret, may form the key to unlock the secrets of all Nature.

This "I am," or "I exist" is uncontradictable, undeniable, and is infallible knowledge. Everything else is liable and prone to modification, or even contradiction. But, the knowledge of "I am" is mystical; it needs the support of nothing else.

Is this the Reality that man is searching for? Does this stand the test of truth?

Human existence is characterised by a series of experiences, all of which may be classified into the state of waking, dream and deep sleep. The conclusion, or knowledge of "I am" is obtained in the waking state. Does man, the "I", exist in the other states? Can one conclusively say "I am", with reference to all these states? The question appears superfluous, and the answer is self evident, because, if these states are states of experience, as mentioned, there must be an experiencer, the self, the "I". So, the answer is "I exist". Thus, if the "I exist" can be emphatically said to be true for all states of experience, how does the "I" exist in these states? What is the true nature of the self which affirms "I am" and which passes through these states?