Chapter II: Part 2

There can, therefore, be no question of putting thought and feeling on a level as objects of observation. And the same could easily be shown of other activities of the human mind. Unlike thought, they must be classed with any other observed objects or events. The peculiar nature of thought lies just in this, that it is an activity which is directed solely on the observed object and not on the thinking subject. This is apparent even from the way in which we express our thoughts about an object, as distinct from our feelings or acts of will. When I see an object and recognise it as a table, I do not as a rule say, "I am thinking of a table," but, "this is a table." On the other hand, I do say, "I am pleased with the table." In the former case, I am not at all interested in stating that I have entered into a relation with the table; whereas, in the second case, it is just this relation which matters. In saying, "I am thinking of a table," I adopt the exceptional point of view characterised above, in which something is made the object of observation which is always present in our mental activity, without being itself normally an observed object.

The peculiar nature of thought consists just in this, that the thinker forgets his thinking while actually engaged in it. It is not thinking which occupies his attention, but rather the object of thought which he observes.

The first point, then, to notice about thought is that it is the unobserved element in our ordinary mental life.

The reason why we do not notice the thinking which goes on in our ordinary mental life is no other than this, that it is our own activity. Whatever I do not myself produce appears in my field of consciousness as an object; I contrast it with myself as something the existence of which is independent of me. It forces itself upon me. I must accept it as the presupposition of my thinking. As long as I think about the object, I am absorbed in it, my attention is turned on it. To be thus absorbed in the object is just to contemplate it by thought. I attend, not to my activity, but to its object. In other words, whilst I am thinking I pay no heed to my thinking which is of my own making, but only to the object of my thinking which is not of my making.

I am, moreover, in exactly the same position when I adopt the exceptional point of view and think of my own thought-processes. I can never observe my present thought, I can only make my past experiences of thought-processes subsequently the objects of fresh thoughts. If I wanted to watch my present thought, I should have to split myself into two persons, one to think, the other to observe this thinking. But this is impossible. I can only accomplish it in two separate acts. The observed thought-processes are never those in which I am actually engaged but others. Whether, for this purpose, I make observations on my own former thoughts, or follow the thought-processes of another person, or finally, as in the example of the motions of the billiard balls, assume an imaginary thought-process, is immaterial.

There are two things which are incompatible with one another: productive activity and the theoretical contemplation of that activity. This is recognised even in the First Book of Moses. It represents God as creating the world in the first six days, and only after its completion is any contemplation of the world possible: "And God saw everything that he had made and, behold, it was very good." The same applies to our thinking. It must be there first, if we would observe it.

The reason why it is impossible to observe the thought-process in its actual occurrence at any given moment, is the same as that which makes it possible for us to know it more immediately and more intimately than any other process in the world. Just because it is our own creation do we know the characteristic features of its course, the manner in which the process, in detail, takes place. What in the other spheres of observation we can discover only indirectly, viz., the relevant objective nexus and the relations of the individual objects, that is known to us immediately in the case of thought. I do not know off-hand why, for perception, thunder follows lightning, but I know immediately, from the content of the two concepts, why my thought connects the concept of thunder with that of lightning. It does not matter for my argument whether my concepts of thunder and lightning are correct. The connection between the concepts I have is clear to me, and that through the very concepts themselves.

This transparent clearness in the observation of our thought-processes is quite independent of our knowledge of the physiological basis of thought. I am speaking here of thought in the sense in which it is the object of our observation of our own mental activity. For this purpose it is quite irrelevant how one material process in my brain causes or influences another, whilst I am carrying on a process of thought. What I observe, in studying a thought-process, is, not what process in my brain connects the concept of thunder with that of lightning, but what is my reason for bringing these two concepts into a definite relation. Introspection shows that, in linking thought with thought, I am guided by their content, not by the material processes in the brain. This remark would be quite superfluous in a less materialistic age than ours. To-day, however, when there are people who believe that, when we know what matter is, we shall know also how it thinks, it is necessary to affirm the possibility of speaking of thought without trespassing on the domain of brain physiology. Many people to-day find it difficult to grasp the concept of thought in its purity. Anyone who challenges the account of thought which I have given here, by quoting Cabanis' statement that "the brain secretes thoughts as the liver does gall or the spittle-glands spittle, etc." simply does not know of what I am talking. He attempts to discover thought by the same method of mere observation which we apply to the other objects that make up the world. But he cannot find it in this way, because, as I have shown, it eludes just this ordinary observation. Whoever cannot transcend Materialism lacks the ability to throw himself into the exceptional attitude I have described, in which he becomes conscious of what in all other mental activity remains unconscious. It is as useless to discuss thought with one who is not willing to adopt this attitude, as it would be to discuss colour with a blind man. Let him not imagine, however, that we regard physiological processes as thought. He fails to explain thought, because he is not even aware that it is there.

For every one, however, who has the ability to observe thought, and with good will every normal man has this ability, this observation is the most important he can make. For he observes something which he himself produces. He is not confronted by what is to begin with a strange object, but by his own activity. He knows how that which he observes has come to be. He perceives clearly its connections and relations. He gains a firm point from which he can, with well-founded hopes, seek an explanation of the other phenomena of the world.

The feeling that he had found such a firm foundation, induced the father of modern philosophy, Descartes, to base the whole of human knowledge on the principle, "I think, therefore I am." All other things, all other processes, are independent of me. Whether they be truth, or illusion, or dream, I know not. There is only one thing of which I am absolutely certain, for I myself am the author of its indubitable existence; and that is my thought. Whatever other origin it may have in addition, whether it come from God or from elsewhere, of one thing I am sure, that it exists in the sense that I myself produce it. Descartes had, to begin with, no justification for reading any other meaning into his principle. All he had a right to assert was that, in apprehending myself as thinking, I apprehend myself, within the world-system, in that activity which is most uniquely characteristic of me. What the added words "therefore I am" are intended to mean has been much debated. They can have a meaning on one condition only. The simplest assertion I can make of a thing is, that it is, that it exists. What kind of existence, in detail, it has, can in no case be determined on the spot, as soon as the thing enters within the horizon of my experience. Each object must be studied in its relations to others, before we can determine the sense in which we can speak of its existence. An experienced process may be a complex of percepts, or it may be a dream, an hallucination, etc. In short, I cannot say in what sense it exists. I can never read off the kind of existence from the process itself, for I can discover it only when I consider the process in its relation to other things. But this, again, yields me no knowledge beyond just its relation to other things. My inquiry touches firm ground only when I find an object, the reason of the existence of which I can gather from itself. Such an object I am myself in so far as I think, for I qualify my existence by the determinate and self-contained content of my thought-activity. From here I can go on to ask whether other things exist in the same or in some other sense.

When thought is made an object of observation, something which usually escapes our attention is added to the other observed contents of the world. But the usual manner of observation, such as is employed also for other objects, is in no way altered. We add to the number of objects of observation, but not to the number of methods. When we are observing other things, there enters among the world-processes--among which I now include observation--one process which is overlooked. There is present something different from every other kind of process, something which is not taken into account. But when I make an object of my own thinking, there is no such neglected element present. For what lurks now in the background is just thought itself over again. The object of observation is qualitatively identical with the activity directed upon it. This is another characteristic feature of thought-processes. When we make them objects of observation, we are not compelled to do so with the help of something qualitatively different, but can remain within the realm of thought.

When I weave a tissue of thoughts round an independently given object, I transcend my observation, and the question then arises, What right have I to do this? Why do I not passively let the object impress itself on me? How is it possible for my thought to be relevantly related to the object? These are questions which every one must put to himself who reflects on his own thought-processes. But all these questions lapse when we think about thought itself. We then add nothing to our thought that is foreign to it, and therefore have no need to justify any such addition.

Schelling says: "To know Nature means to create Nature." If we take these words of the daring philosopher of Nature literally, we shall have to renounce for ever all hope of gaining knowledge of Nature. For Nature after all exists, and if we have to create it over again, we must know the principles according to which it has originated in the first instance. We should have to borrow from Nature as it exists the conditions of existence for the Nature which we are about to create. But this borrowing, which would have to precede the creating, would be a knowing of Nature, and would be this even if after the borrowing no creation at all were attempted. The only kind of Nature which it would be possible to create without previous knowledge, would be a Nature different from the existing one.

What is impossible with Nature, viz., creation prior to knowledge, that we accomplish in the act of thought. Were we to refrain from thinking until we had first gained knowledge of it, we should never think at all. We must resolutely think straight ahead, and then afterwards by introspective analysis gain knowledge of our own processes. Thus we ourselves create the thought-processes which we then make objects of observation. The existence of all other objects is provided for us without any activity on our part.

My contention that we must think before we can make thought an object of knowledge, might easily be countered by the apparently equally valid contention that we cannot wait with digesting until we have first observed the process of digestion. This objection would be similar to that brought by Pascal against Descartes, when he asserted we might also say "I walk, therefore I am." Certainly I must digest resolutely and not wait until I have studied the physiological process of digestion. But I could only compare this with the analysis of thought if, after digestion, I set myself not to analyse it by thought, but to eat and digest it. It is not without reason that, while digestion cannot become the object of digestion, thought can very well become the object of thought.

This then is indisputable, that in thinking we have got hold of one bit of the world-process which requires our presence if anything is to happen. And that is the very point that matters. The very reason why things seem so puzzling is just that I play no part in their production. They are simply given to me, whereas I know how thought is produced. Hence there can be no more fundamental starting-point than thought from which to regard all world-processes.

I should like still to mention a widely current error which prevails with regard to thought. It is often said that thought, in its real nature, is never experienced. The thought-processes which connect our perceptions with one another, and weave about them a network of concepts, are not at all the same as those which our analysis afterwards extracts from the objects of perception, in order to make them the object of study. What we have unconsciously woven into things is, so we are told, something widely different from what subsequent analysis recovers out of them.

Those who hold this view do not see that it is impossible to escape from thought. I cannot get outside thought when I want to observe it. We should never forget that the distinction between thought which goes on unconsciously and thought which is consciously analysed, is a purely external one and irrelevant to our discussion. I do not in any way alter a thing by making it an object of thought. I can well imagine that a being with quite different sense-organs, and with a differently constructed intelligence, would have a very different idea of a horse from mine, but I cannot think that my own thought becomes different because I make it an object of knowledge. I myself observe my own processes. We are not talking here of how my thought-processes appear to an intelligence different from mine, but how they appear to me. In any case, the idea which another mind forms of my thought cannot be truer than the one which I form myself. Only if the thought-processes were not my own, but the activity of a being quite different from me, could I maintain that, notwithstanding my forming a definite idea of these thought-processes, their real nature was beyond my comprehension.

So far, there is not the slightest reason why I should regard my thought from any other point of view than my own. I contemplate the rest of the world by means of thought. How should I make of my thought an exception?

I think I have given sufficient reasons for making thought the starting-point for my theory of the world. When Archimedes had discovered the lever, he thought he could lift the whole cosmos out of its hinges, if only he could find a point of support for his instrument. He needed a point which was self-supporting. In thought we have a principle which is self-subsisting. Let us try, therefore, to understand the world starting with thought as our basis. Thought can be grasped by thought. The question is whether by thought we can also grasp something other than thought.

I have so far spoken of thought without taking any account of its vehicle, the human consciousness. Most present-day philosophers would object that, before there can be thought, there must be consciousness. Hence we ought to start, not from thought, but from consciousness. There is no thought, they say without consciousness. In reply I would urge that, in order to clear up the relation between thought and consciousness, I must think about it. Hence I presuppose thought. One might, it is true, retort that, though a philosopher who wishes to understand consciousness, naturally makes use of thought, and so far presupposes it, in the ordinary course of life thought arises within consciousness and therefore presupposes that. Were this answer given to the world-creator, when he was about to create thought, it would, without doubt, be to the point. Thought cannot, of course, come into being before consciousness. The philosopher, however, is not concerned with the creation of the world, but with the understanding of it. Hence he is in search of the starting-point, not for creation, but for the understanding of the world. It seems to me very strange that philosophers are reproached for troubling themselves, above all, about the correctness of their principles, instead of turning straight to the objects which they seek to understand. The world-creator had above all to know how to find a vehicle for thought; the philosopher must seek a firm basis for the understanding of what is given. What does it help us to start with consciousness and make it an object of thought, if we have not first inquired how far it is possible at all to gain any knowledge of things by thought?

We must first consider thought quite impartially without relation to a thinking subject or to an object of thought. For subject and object are both concepts constructed by thought. There is no denying that thought must be understood before anything else can be understood. Whoever denies this, fails to realise that man is not the first link in the chain of creation but the last. Hence, in order to explain the world by means of concepts, we cannot start from the elements of existence which came first in time, but we must begin with those which are nearest and most intimately connected with us. We cannot, with a leap, transport ourselves to the beginning of the world, in order to begin our analysis there, but we must start from the present and see whether we cannot advance from the later to the earlier. As long as Geology fabled fantastic revolutions to account for the present state of the earth, it groped in darkness. It was only when it began to study the processes at present at work on the earth, and from these to argue back to the past, that it gained a firm foundation. As long as Philosophy assumes all sorts of principles, such as atom, motion, matter, will, the unconscious, it will hang in the air. The philosopher can reach his goal only if he adopts that which is last in time as first in his theory. This absolutely last in the world-process is thought.

There are people who say it is impossible to ascertain with certainty whether thought is right or wrong, and that, so far, our starting-point is a doubtful one. It would be just as intelligent to raise doubts as to whether a tree is in itself right or wrong. Thought is a fact, and it is meaningless to speak of the truth or falsity of a fact. I can, at most, be in doubt as to whether thought is rightly employed, just as I can doubt whether a certain tree supplies wood adapted to the making of this or that useful object. It is just the purpose of this book to show how far the application of thought to the world is right or wrong. I can understand anyone doubting whether, by means of thought, we can gain any knowledge of the world, but it is unintelligible to me how anyone can doubt that thought in itself is right.

ADDITION TO THE REVISED EDITION (1918).

In the preceding discussion I have pointed out the importance of the difference between thinking and all other activities of mind. This difference is a fact which is patent to genuinely unprejudiced observation. An observer who does not try to see the facts without preconception will be tempted to bring against my argumentation such objections as these: When I think about a rose, there is involved nothing more than a relation of my "I" to the rose, just as when I feel the beauty of the rose. There subsists a relation between "I" and object in thinking precisely as there does, e.g., in feeling or perceiving. Those who urge this objection fail to bear in mind that it is only in the activity of thinking that the "I," or Ego, knows itself to be identical, right into all the ramifications of the activity, with that which does the thinking. Of no other activity of mind can we say the same. For example, in a feeling of pleasure it is easy for a really careful observer to discriminate between the extent to which the Ego knows itself to be identical with what is active in the feeling, and the extent to which there is something passive in the Ego, so that the pleasure is merely something which happens to the Ego. The same applies to the other mental activities. The main thing is not to confuse the "having of images" with the elaboration of ideas by thinking. Images may appear in the mind dream-wise, like vague intimations. But this is not thinking. True, someone might now urge: If this is what you mean by "thinking," then your thinking contains willing, and you have to do, not with mere thinking, but with the will to think. However, this would justify us only in saying: Genuine thinking must always be willed thinking. But this is quite irrelevant to the characterisation of thinking as this has been given in the preceding discussion. Let it be granted that the nature of thinking necessarily implies its being willed, the point which matters is that nothing is willed which, in being carried out, fails to appear to the Ego as an activity completely its own and under its own supervision. Indeed, we must say that thinking appears to the observer as through and through willed, precisely because of its nature as above defined. If we genuinely try to master all the facts which are relevant to a judgment about the nature of thinking, we cannot fail to observe that, as a mental activity, thinking has the unique character which is here in question.

A reader of whose powers the author of this book has a very high opinion, has objected that it is impossible to speak about thinking as we are here doing, because the supposed observation of active thinking is nothing but an illusion. In reality, what is observed is only the results of an unconscious activity which lies at the basis of thinking. It is only because, and just because, this unconscious activity escapes observation, that the deceptive appearance of the self-existence of the observed thinking arises, just as when an illumination by means of a rapid succession of electric sparks makes us believe that we see a movement. This objection, likewise, rests solely on an inaccurate view of the facts. The objection ignores that it is the Ego itself which, identical with the thinking, observes from within its own activity. The Ego would have to stand outside the thinking in order to suffer the sort of deception which is caused by an illumination with a rapid succession of electric sparks. One might say rather that to indulge in such an analogy is to deceive oneself wilfully, just as if someone, seeing a moving light, were obstinately to affirm that it is being freshly lit by an unknown hand at every point where it appears. No, whoever is bent on seeing in thought anything else than an activity produced--and observable by--the Ego has first to shut his eyes to the plain facts that are there for the looking, in order then to invent a hypothetical activity as the basis of thinking. If he does not wilfully blind himself, he must recognise that all these "hypothetical additions" to thinking take him away from its real nature. Unprejudiced observation shows that nothing is to be counted as belonging to the nature of thinking except what is found in thinking itself. It is impossible to discover the cause of thinking by going outside the realm of thought.

IV

THE WORLD AS PERCEPT

The products of thinking are concepts and ideas. What a concept is cannot be expressed in words. Words can do no more than draw our attention to the fact that we have concepts. When someone perceives a tree, the perception acts as a stimulus for thought. Thus an ideal element is added to the perceived object, and the perceiver regards the object and its ideal complement as belonging together. When the object disappears from the field of his perception, the ideal counterpart alone remains. This latter is the concept of the object. The wider the range of our experience, the larger becomes the number of our concepts. Moreover, concepts are not by any means found in isolation one from the other. They combine to form an ordered and systematic whole. The concept "organism," e.g., combines with those of "development according to law," "growth," and others. Other concepts based on particular objects fuse completely with one another. All concepts formed from particular lions fuse in the universal concept "lion." In this way, all the separate concepts combine to form a closed, conceptual system within which each has its special place. Ideas do not differ qualitatively from concepts. They are but fuller, more saturated, more comprehensive concepts. I attach special importance to the necessity of bearing in mind, here, that I make thought my starting-point, and not concepts and ideas which are first gained by means of thought. These latter presuppose thought. My remarks regarding the self-dependent, self-sufficient character of thought cannot, therefore, be simply transferred to concepts. (I make special mention of this, because it is here that I differ from Hegel, who regards the concept as something primary and ultimate.)

Concepts cannot be derived from perception. This is apparent from the fact that, as man grows up, he slowly and gradually builds up the concepts corresponding to the objects which surround him. Concepts are added to perception.

A philosopher, widely read at the present day (Herbert Spencer), describes the mental process which we perform upon perception as follows: "If, when walking through the fields some day in September, you hear a rustle a few yards in advance, and on observing the ditch-side where it occurs, see the herbage agitated, you will probably turn towards the spot to learn by what this sound and motion are produced. As you approach there flutters into the ditch a partridge; on seeing which your curiosity is satisfied--you have what you call an explanation of the appearances. The explanation, mark, amounts to this--that whereas throughout life you have had countless experiences of disturbance among small stationary bodies, accompanying the movement of other bodies among them, and have generalised the relation between such disturbances and such movements, you consider this particular disturbance explained on finding it to present an instance of the like relation" (First Principles, Part I, par. 23). A closer analysis leads to a very different description from that here given. When I hear a noise, my first demand is for the concept which fits this percept. Without this concept, the noise is to me a mere noise. Whoever does not reflect further, hears just the noise and is satisfied with that. But my thought makes it clear to me that the noise is to be regarded as an effect. Thus it is only when I combine the concept of effect with the percept of a noise that I am led to go beyond the particular percept and seek for its cause. The concept of "effect" calls up that of "cause," and my next step is to look for the agent, which I find, say, in a partridge. But these concepts, cause and effect, can never be gained through mere perception, however many instances we bring under review. Perception evokes thought, and it is this which shows me how to link separate experiences together.

If one demands of a "strictly objective science" that it should take its data from perception alone, one must demand also that it abandon all thought. For thought, by its very nature, transcends the objects of perception.

It is time now to pass from thought to the thinker. For it is through the thinker that thought and perception are combined. The human mind is the stage on which concept and percept meet and are linked to one another. In saying this, we already characterise this (human) consciousness. It mediates between thought and perception. In perception the object appears as given, in thought the mind seems to itself to be active. It regards the thing as object and itself as the thinking subject. When thought is directed upon the perceptual world we have consciousness of objects; when it is directed upon itself we have self-consciousness. Human consciousness must, of necessity, be at the same time self-consciousness, because it is a consciousness which thinks. For, when thought contemplates its own activity it makes an object for study of its own essential nature, it makes an object of itself as subject.

It is important to note here that it is only by means of thinking that I am able to determine myself as subject and contrast myself with objects. Therefore thinking must never be regarded as a merely subjective activity. Thinking transcends the distinction of subject and object. It produces these two concepts just as it produces all others. When, therefore, I, as thinking subject, refer a concept to an object, we must not regard this reference as something purely subjective. It is not the subject, but thought, which makes the reference. The subject does not think because it is a subject, rather it conceives itself to be a subject because it can think. The activity of consciousness, in so far as it thinks, is thus not merely subjective. Rather it is neither subjective nor objective; it transcends both these concepts. I ought never to say that I, as an individual subject, think, but rather that I, as subject, exist myself by the grace of thought. Thought thus takes me out of myself and relates me to objects. At the same time it separates me from them, inasmuch as I, as subject, am set over against the objects.

It is just this which constitutes the double nature of man. His thought embraces himself and the rest of the world. But by this same act of thought he determines himself also as an individual, in contrast with the objective world.

We must next ask ourselves how the other element, which we have so far simply called the perceptual object and which comes, in consciousness, into contact with thought, enters into thought at all?

In order to answer this question, we must eliminate from the field of consciousness everything which has been imported by thought. For, at any moment, the content of consciousness is always shot through with concepts in the most various ways.

Let us assume that a being with fully developed human intelligence originated out of nothing and confronted the world. All that it there perceived before its thought began to act would be the pure content of perception. The world so far would appear to this being as a mere chaotic aggregate of sense-data, colours, sounds, sensations of pressure, of warmth, of taste, of smell, and, lastly, feelings of pleasure and pain. This mass constitutes the world of pure unthinking perception. Over against it stands thought, ready to begin its activity as soon as it can find a point of attack. Experience shows that the opportunity is not long in coming. Thought is able to draw threads from one sense-datum to another. It brings definite concepts to bear on these data and thus establishes a relation between them. We have seen above how a noise which we hear is connected with another content by our identifying the first as the effect of the second.

If now we recollect that the activity of thought is on no account to be considered as merely subjective, then we shall not be tempted to believe that the relations thus established by thought have merely subjective validity.

Our next task is to discover by means of thought what relation the above-mentioned immediate sense-data have to the conscious subject.

The ambiguity of current speech makes it advisable for me to come to an agreement with my readers concerning the meaning of a word which I shall have to employ in what follows. I shall apply the name "percepts" to the immediate sense-data enumerated above, in so far as the subject consciously apprehends them. It is, then, not the process of perception, but the object of this process which I call the "percept."

I reject the term "sensation," because this has a definite meaning in Physiology which is narrower than that of my term "percept." I can speak of feeling as a percept, but not as a sensation in the physiological sense of the term. Before I can have cognisance of my feeling it must become a percept for me. The manner in which, through observation, we gain knowledge of our thought-processes is such that when we first begin to notice thought, it too may be called a percept.

The unreflective man regards his percepts, such as they appear to his immediate apprehension, as things having a wholly independent existence. When he sees a tree he believes that it stands in the form which he sees, with the colours of all its parts, etc., there on the spot towards which his gaze is directed. When the same man sees the sun in the morning appear as a disc on the horizon, and follows the course of this disc, he believes that the phenomenon exists and occurs (by itself) exactly as he perceives it. To this belief he clings until he meets with further percepts which contradict his former ones. The child who has as yet had no experience of distance grasps at the moon, and does not correct its first impression as to the real distance until a second percept contradicts the first. Every extension of the circle of my percepts compels me to correct my picture of the world. We see this in everyday life, as well as in the mental development of mankind. The picture which the ancients made for themselves of the relation of the earth to the sun and other heavenly bodies, had to be replaced by another when Copernicus found that it contradicted percepts which in those early days were unknown. A man who had been born blind said, when operated on by Dr. Franz, that the idea of the size of objects which he had formed before his operation by his sense of touch was a very different one. He had to correct his tactual percepts by his visual percepts.

How is it that we are compelled to make these continual corrections in our observations?

A single reflection supplies the answer to this question. When I stand at one end of an avenue, the trees at the other end, away from me, seem smaller and nearer together than those where I stand. But the scene which I perceive changes when I change the place from which I am looking. The exact form in which it presents itself to me is, therefore, dependent on a condition which inheres, not in the object, but in me, the percipient. It is all the same to the avenue where I stand. But the picture of it which I receive depends essentially on my standpoint. In the same way, it makes no difference to the sun and the planetary system that human beings happen to perceive them from the earth; but the picture of the heavens which human beings have is determined by the fact that they inhabit the earth. This dependence of our percepts on our points of observation is the easiest kind of dependence to understand. The matter becomes more difficult when we realise further that our perceptual world is dependent on our bodily and mental organisation. The physicist teaches us that within the space in which we hear a sound there are vibrations of the air, and that there are vibrations also in the particles of the body which we regard as the cause of the sound. These vibrations are perceived as sounds only if we have normally constructed ears. Without them the whole world would be for us for ever silent. Again, the physiologist teaches us that there are men who perceive nothing of the wonderful display of colours which surrounds us. In their world there are only degrees of light and dark. Others are blind only to one colour, e.g., red. Their world lacks this colour tone, and hence it is actually a different one from that of the average man. I should like to call the dependence of my perceptual world on my point of observation "mathematical," and its dependence on my organisation "qualitative." The former determines proportions of size and mutual distances of my percepts, the latter their quality. The fact that I see a red surface as red--this qualitative determination--depends on the structure of my eye.

My percepts, then, are in the first instance subjective. The recognition of the subjective character of our percepts may easily lead us to doubt whether there is any objective basis for them at all. When we know that a percept, e.g., that of a red colour or of a certain tone, is not possible without a specific structure of our organism, we may easily be led to believe that it has no being at all apart from our subjective organisation, that it has no kind of existence apart from the act of perceiving of which it is the object. The classical representative of this theory is George Berkeley, who held that from the moment we realise the importance of a subject for perception, we are no longer able to believe in the existence of a world apart from a conscious mind. "Some truths there are so near and obvious to the mind that man need only open his eyes to see them. Such I take this important one to be, viz., that all the choir of heaven and the furniture of the earth--in a word, all those bodies which compose the mighty frame of the world--have not any subsistence without a mind; that their being is to be perceived or known; that consequently, so long as they are not actually perceived by me, or do not exist in my mind or that of any other created spirit, they must either have no existence at all or else subsist in the mind of some Eternal Spirit" (Berkeley, Of the Principles of Human Knowledge, Part I, Section 6).

On this view, when we take away the act of perceiving, nothing remains of the percept. There is no colour when none is seen, no sound when none is heard. Extension, form, and motion exist as little as colour and sound apart from the act of perception. We never perceive bare extension or shape. These are always joined with colour or some other quality, which are undoubtedly dependent on the subject. If these latter disappear when we cease to perceive, the former, being connected with them, must disappear likewise.

If it is urged that, even though figure, colour, sound, etc., have no existence except in the act of perception, yet there must be things which exist apart from perception and which are similar to the percepts in our minds, then the view we have mentioned would answer, that a colour can be similar only to a colour, a figure to a figure. Our percepts can be similar only to our percepts and to nothing else. Even what we call a thing is nothing but a collection of percepts which are connected in a definite way. If I strip a table of its shape, extension, colour, etc.--in short, of all that is merely my percepts--then nothing remains over. If we follow this view to its logical conclusion, we are led to the assertion that the objects of my perceptions exist only through me, and only in as far as, and as long as, I perceive them. They disappear with my perceiving and have no meaning apart from it. Apart from my percepts I know of no objects and cannot know of any.

No objection can be made to this assertion as long as we take into account merely the general fact that the percept is determined in part by the organisation of the subject. The matter would be far otherwise if we were in a position to say what part exactly is played by our perceiving in the occurrence of a percept. We should know then what happens to a percept whilst it is being perceived, and we should also be able to determine what character it must possess before it comes to be perceived.

This leads us to turn our attention from the object of a perception to the subject of it. I am aware not only of other things but also of myself. The content of my perception of myself consists, in the first instance, in that I am something stable in contrast with the ever coming and going flux of percepts. The awareness of myself accompanies in my consciousness the awareness of all other percepts. When I am absorbed in the perception of a given object I am, for the time being, aware only of this object. Next I become aware also of myself. I am then conscious, not only of the object, but also of my Self as opposed to and observing the object. I do not merely see a tree, I know also that it is I who see it. I know, moreover, that some process takes place in me when I observe a tree. When the tree disappears from my field of vision, an after-effect of this process remains, viz., an image of the tree. This image has become associated with my Self during my perception. My Self has become enriched; to its content a new element has been added. This element I call my idea of the tree. I should never have occasion to talk of ideas, were I not aware of my own Self. Percepts would come and go; I should let them slip by. It is only because I am aware of my Self, and observe that with each perception the content of the Self is changed, that I am compelled to connect the perception of the object with the changes in the content of my Self, and to speak of having an idea.

That I have ideas is in the same sense matter of observation to me as that other objects have colour, sound, etc. I am now also able to distinguish these other objects, which stand over against me, by the name of the outer world, whereas the contents of my perception of my Self form my inner world. The failure to recognise the true relation between idea and object has led to the greatest misunderstandings in modern philosophy. The fact that I perceive a change in myself, that my Self undergoes a modification, has been thrust into the foreground, whilst the object which causes these modifications is altogether ignored. In consequence it has been said that we perceive, not objects, but only our ideas. I know, so it is said, nothing of the table in itself, which is the object of my perception, but only of the changes which occur within me when I perceive a table. This theory should not be confused with the Berkeleyan theory mentioned above. Berkeley maintains the subjective nature of my perceptual contents, but he does not say that I can know only my own ideas. He limits my knowledge to my ideas because, on his view, there are no objects other than ideas. What I perceive as a table no longer exists, according to Berkeley, when I cease to look at it. This is why Berkeley holds that our percepts are created directly by the omnipotence of God. I see a table because God causes this percept in me. For Berkeley, therefore, nothing is real except God and human spirits. What we call the "world" exists only in spirits. What the naïve man calls the outer world, or material nature, is for Berkeley non-existent. This theory is confronted by the now predominant Kantian view which limits our knowledge of the world to our ideas, not because of any conviction that nothing beyond these ideas exists, but because it holds that we are so organised that we can have knowledge only of the changes within our own selves, not of the things-in-themselves which are the causes of these changes. This view concludes from the fact that I know only my own ideas, not that there is no reality independent of them, but only that the subject cannot have direct knowledge of such reality. The mind can merely "through the medium of its subjective thoughts imagine it, conceive it, know it, or perhaps also fail to know it" (O. Liebmann, Zur Analysis der Wirklichkeit, p. 28). Kantians believe that their principles are absolutely certain, indeed immediately evident, without any proof. "The most fundamental principle which the philosopher must begin by grasping clearly, consists in the recognition that our knowledge, in the first instance, does not extend beyond our ideas. Our ideas are all that we immediately have and experience, and just because we have immediate experience of them the most radical doubt cannot rob us of this knowledge. On the other hand, the knowledge which transcends my ideas--taking ideas here in the widest possible sense, so as to include all psychical processes--is not proof against doubt. Hence, at the very beginning of all philosophy we must explicitly set down all knowledge which transcends ideas as open to doubt." These are the opening sentences of Volkelt's book on Kant's Theory of Knowledge. What is here put forward as an immediate and self-evident truth is, in reality, the conclusion of a piece of argument which runs as follows. Naïve common sense believes that things, just as we perceive them, exist also outside our minds. Physics, Physiology, and Psychology, however, teach us that our percepts are dependent on our organisation, and that therefore we cannot know anything about external objects except what our organisation transmits to us. The objects which we perceive are thus modifications of our organisation, not things-in-themselves. This line of thought has, in fact, been characterised by Ed. von Hartmann as the one which leads necessarily to the conviction that we can have direct knowledge only of our own ideas (cp. his Grundproblem der Erkenntnistheorie, pp. 16-40). Because outside our organisms we find vibrations of particles and of air, which are perceived by us as sounds, it is concluded that what we call sound is nothing more than a subjective reaction of our organisms to these motions in the external world. Similarly, colour and heat are inferred to be merely modifications of our organisms. And, further, these two kinds of percepts are held to be the effects of processes in the external world which are utterly different from what we experience as heat or as colour. When these processes stimulate the nerves in the skin of my body, I perceive heat; when they stimulate the optical nerve I perceive light and colour. Light, colour, and heat, then, are the reactions of my sensory nerves to external stimuli. Similarly, the sense of touch reveals to me, not the objects of the outer world, but only states of my own body. The physicist holds that bodies are composed of infinitely small particles called molecules, and that these molecules are not in direct contact with one another, but have definite intervals between them. Between them, therefore, is empty space. Across this space they act on one another by attraction and repulsion. If I put my hand on a body, the molecules of my hand by no means touch those of the body directly, but there remains a certain distance between body and hand, and what I experience as the body's resistance is nothing but the effect of the force of repulsion which its molecules exert on my hand. I am absolutely external to the body and experience only its effects on my organism.

The theory of the so-called Specific Nervous Energy, which has been advanced by J. Müller, supplements these speculations. It asserts that each sense has the peculiarity that it reacts to all external stimuli in only one definite way. If the optic nerve is stimulated, light sensations result, irrespective of whether the stimulation is due to what we call light, or to mechanical pressure, or an electrical current. On the other hand, the same external stimulus applied to different senses gives rise to different sensations. The conclusion from these facts seems to be, that our sense-organs can give us knowledge only of what occurs in themselves, but not of the external world. They determine our percepts, each according to its own nature.

Physiology shows, further, that there can be no direct knowledge even of the effects which objects produce on our sense-organs. Through his study of the processes which occur in our own bodies, the physiologist finds that, even in the sense-organs, the effects of the external process are modified in the most diverse ways. We can see this most clearly in the case of eye and ear. Both are very complicated organs which modify the external stimulus considerably, before they conduct it to the corresponding nerve. From the peripheral end of the nerve the modified stimulus is then conducted to the brain. Here the central organs must in turn be stimulated. The conclusion is, therefore, drawn that the external process undergoes a series of transformations before it reaches consciousness. The brain processes are connected by so many intermediate links with the external stimuli, that any similarity between them is out of the question. What the brain ultimately transmits to the soul is neither external processes, nor processes in the sense-organs, but only such as occur in the brain. But even these are not apprehended immediately by the soul. What we finally have in consciousness are not brain processes at all, but sensations. My sensation of red has absolutely no similarity with the process which occurs in the brain when I sense red. The sensation, again, occurs as an effect in the mind, and the brain process is only its cause. This is why Hartmann (Grundproblem der Erkenntnistheorie, p. 37) says, "What the subject experiences is therefore only modifications of his own psychical states and nothing else." However, when I have sensations, they are very far as yet from being grouped in those complexes which I perceive as "things." Only single sensations can be transmitted to me by the brain. The sensations of hardness and softness are transmitted to me by the organ of touch, those of colour and light by the organ of sight. Yet all these are found united in one object. This unification must, therefore, be brought about by the soul itself; that is, the soul constructs things out of the separate sensations which the brain conveys to it. My brain conveys to me singly, and by widely different paths, the visual, tactual, and auditory sensations which the soul then combines into the idea of a trumpet. Thus, what is really the result of a process (i.e., the idea of a trumpet), is for my consciousness the primary datum. In this result nothing can any longer be found of what exists outside of me and originally stimulated my sense-organs. The external object is lost entirely on the way to the brain and through the brain to the soul.