FROM THE FOREGOING considerations it follows that by investigating the content of our observation it is impossible to prove that our perceptions are representations. This proof is supposed to follow from the fact that if the process of perception takes place in the way it is imagined, according to the naive-realistic suppositions as to man's psychological and physiological constitution, then we are dealing, not with things-in-themselves, but merely with our representations of things. Now if naive realism, when consistently thought through, leads to results which directly contradict what it presupposes, then one must regard its presuppositions as unsuitable for the foundation of a world view and discard them. It is certainly inadmissible on the one hand to reject the presuppositions and yet, on the other, to regard their outcome as valid, as does the critical idealist when he bases his assertion, The world is my representation, on the so-called proof indicated above. (Eduard von Hartmann gives a full account of this line of argument in his work, Das Grundproblem der Erkenntnistheorie, The Basic Problem of a Theory of Knowledge.)
The correctness of critical idealism is one thing, the power of conviction of its proof another. How it stands with the former will be seen later in the course of our discussion. But the power of conviction of its proof is nil. If one builds a house and the first floor collapses while the second floor is being built, then the second floor collapses also. As first floor is related to second floor, so is naive realism related to critical idealism.
For the one holding the view that the whole world we perceive is only a world that we represent to ourselves and, indeed, only the effect on our soul of things unknown to us, the essential problem of knowledge is naturally concerned, not with the representations present only in the soul, but with the things which lie outside our consciousness and are independent of us. He asks: How much can we indirectly learn about them, since they are not directly accessible to our observation? From this point of view he is concerned, not with the inner connection of his conscious perceptions, but with their causes, which lie beyond his consciousness and exist independently of him while the perceptions disappear as soon as he turns his senses away from things. From this point of view, our consciousness acts like a mirror from which the pictures of things also disappear the moment its reflecting surface is not turned toward them. He who does not see things themselves, but only their reflections, must obtain information about their nature indirectly by drawing conclusions from the behavior of the reflections. This is the standpoint of modern natural science, which uses perceptions only as a means of obtaining information about the processes of matter which lie behind them, and alone really “are.” If the philosopher, as critical idealist, acknowledges a real existence at all, then his sole aim is to gain knowledge of this real existence indirectly by means of his representations. His interest skips over the subjective world of representations and instead pursues what produces these representations.
But the critical idealist may go as far as to say: I am confined to the world of my representations and cannot get beyond it. If I think that there is something behind my representations, then again this thought is nothing but my representation. An idealist of this kind will then either deny the thing-in-itself entirely or, at any rate, say that it has no significance for human beings, that it is as good as non-existent since we can know nothing of it.
To this kind of critical idealist the whole world seems a dream, in the face of which all striving for knowledge is simply meaningless. For him there can be only two kinds of men: those who are victims of the illusion that their own dream-pictures are real things, and the wise ones who see through the nothingness of this dream-world and therefore must gradually lose all desire to trouble themselves further about it. From this point of view, even one's own personality may become a mere dream phantom. Just as during sleep, among our dream-images an image of our self appears, so in waking consciousness the representation of the I is added to the representations of the outer world. We then have in consciousness not the real I, but only our representation of the I. Now, if the existence of things is denied or at least it is denied that we can know anything of them, then the existence or the knowledge of one's own personality must also be denied. The critical idealist then comes to maintain: “All reality transforms itself into a wonderful dream — without a life which is dreamed about, and without a spirit which dreams — into a dream which hangs together in a dream of itself.” 
It does not matter whether the person who believes that he recognizes life to be a dream assumes nothing more behind this dream, or whether he refers his representations to real things: in either case, life must lose all scientific interest for him. But whereas all science must be meaningless for those who believe that the whole of the accessible universe is exhausted in dreams, for others who believe they can draw conclusions about the things from the representations, science will consist in the investigation of such “things-in-themselves.” The first world view could be described as absolute illusionism, the second is called transcendental realism by its most consistent exponent, Eduard von Hartmann. 
Both these views have this in common with naive realism that they seek to establish themselves by means of an investigation of perceptions. However, nowhere within this sphere can they find a firm foundation.
An essential question for an adherent of transcendental realism must be: How does the I bring about, out of itself, the world of representations? Insofar as it would be a means of investigating indirectly the world of the I-in-itself, an earnest striving for knowledge could still be kindled by a world of representations that was given us, even if this disappeared as soon as we shut our senses to the external world. If the things we experience were representations, then everyday life would be like a dream, and recognition of the true situation would be like an awakening. Our dream pictures also interest us as long as we are dreaming and, consequently, do not recognize them as dreams. The moment we awaken we no longer look for inner connections between our dream-pictures, but for the physical, physiological and psychological processes which caused them. In the same way a philosopher who considers the world to be his representation cannot be interested in the inner connection of the details within it. If he allows for the existence of an I at all, then he will not ask how his representations are connected with one another, but what takes place in the soul that exists independently of him while his consciousness contains a certain content of representations. If I dream that I am drinking wine which makes my throat burn, and I wake up coughing,  then the moment I awaken I cease to be interested in what the dream was about; now my attention is concerned only with the physiological and psychological processes by means of which the irritation which caused me to cough comes to be symbolically expressed in the dream picture. Similarly the philosopher, as soon as he is convinced that the given world consists of nothing but representations, would at once turn from them to the real soul behind them. Things become worse when illusionism completely denies the existence of the I-in-itself behind representations, or at least holds it to be unknowable. One may easily arrive at such a view through the observation that in contrast to dreaming there exists the waking state, in which we have the opportunity to see through the dream and to refer it to the real connections of things, but that we have no condition which is related similarly to our waking conscious life. To adopt this view is to fail to see that in fact there is something which is related to mere perceiving as waking experience is related to dreams. This something is thinking.
The naive man cannot be considered to lack the insight referred to here. He takes the world as it is and regards things as real in the sense in which he experiences them to be so. The first step, however, which is taken beyond this standpoint can only consist in asking: How is thinking related to perception? Whether or not the perception, in the form given me, continues to exist before and after my forming a representation of it, — if I want to say anything whatever about it, I can do so only with the help of thinking. If I say: The world is my representation, I have expressed the result of a thinking process, and if my thinking is not applicable to the world, then this result is erroneous. Between a perception and any kind of assertion about it, thinking slips in.
It has already been indicated why, in our consideration of things, we usually overlook thinking (See p. 61f.). This is due to the fact that we direct our attention only toward the object about which we think, but not toward our thinking at the same time. Naive consciousness treats thinking as something which has nothing to do with things, but stands altogether aloof from them and contemplates them. The picture which the thinker makes of the phenomena of the world is considered, not as something belonging to them, but as something existing only in men's heads. The world is complete, even without this picture The world is finished and ready-made with all its substances and forces, and of this ready-made world man makes himself a picture. Whoever thinks along these lines should be asked: What gives you the right to declare the world to be complete without thinking? Does the world not produce thinking in the heads of men with the same necessity as it produces the blossom on a plant? Plant a seed in the earth. Root and stem will grow. It will unfold leaves and blossoms. Then place the plant before you. In your soul it connects itself with a definite concept. Why should this concept belong to the entire plant any less than leaf and blossom? You say: The leaves and blossoms are there without the presence of a perceiving subject; the concept, however, does not appear till a human being confronts the plant. Quite true. But leaves and blossoms appear on the plant only if there is soil in which the seed can be planted, and light and air in which the leaves and blossoms can unfold. In just this way does the concept of the plant arise when a thinking consciousness confronts it.
It is quite arbitrary to regard as a totality, as a thing in its entirety, the sum of what we experience through mere perception, and to regard as a mere addition, which has nothing to do with the thing itself, what reveals itself through thinking observation. If I receive a rosebud today, the picture that offers itself to my perception is complete only for the moment. If I put the bud into water, tomorrow I shall get a quite different picture of my object. If I do not turn my gaze away from the rosebud, then I shall see today's state gradually change into tomorrow's through an infinite number of intermediate stages. The picture which presents itself to me at any one moment is only a chance section of an object which is in a continual process of becoming. If I do not put the bud into water, a whole series of states, which as possibilities lay within the bud, will not be evolved; or tomorrow I may be prevented from observing the blossom further and therefore will have an incomplete picture of it.
That opinion is quite subjective which, on the basis of a chance picture of a thing, declares: This is the thing.
It is equally inadmissible to declare the sum of perceptions to be the thing. It could well be possible for a being to receive the concept at the same time as, and undivided from, the perception. To such a being it would never occur that the concept did not belong to the thing. He would ascribe to the concept an existence indivisibly bound up with the thing.
Let me make myself clearer by an example. If I throw a stone horizontally through the air, I see it in different places, one after the other. I connect these places to form a line. In mathematics I learn to know various kinds of lines, one of which is the parabola. I know the parabola to be a line produced by a point moving according to certain laws. If I investigate the conditions under which the stone moves, I find that the path traversed is identical with the line I know as a parabola. That the stone moves just in a parabola is a result of the given conditions and necessarily follows from them. The form of the parabola belongs to the whole phenomenon as much as does any other feature of it. The being described above, who did not have to make the detour of thinking, would be given not only a sum of visual aspects at different points but, undivided from the whole occurrence, also the parabolic form of the path which we add to the phenomenon by means of thinking.
It is not due to the objects that they are given us at first without the corresponding concepts, but to our intellectual organization. Our being as a totality functions in such a way that from every reality the elements belonging to it flow to us from two directions: from the direction of perceiving and from that of thinking.
How I am organized for grasping them has nothing to do with the nature of things. The breach between perceiving and thinking is not present until the moment I, the one who contemplates them, confront the things. Which elements do, and which do not belong to the object, cannot at all depend on the manner in which I arrive at knowledge of these elements.
Man is a limited being. To begin with, he is a being among other beings. His existence is bound up with space and time. Because of this, it is always only a limited section of the total universe that can be given him. But this limited section links itself in all directions, both in time and in space, to other sections. If our existence were so bound up with the surrounding world that every process would be a process in us as well, then the distinction between us and things would not exist. But then neither would there be any individual events for us. All events would pass over into one another continuously. The cosmos would be a unity, a totality enclosed within itself. Nowhere would there be a break in the stream of events. It is because of our limitations that things appear to us as if they were separate, when in reality they are not separate at all. Nowhere, for example, is the singular quality of red present by itself, in isolation. It is surrounded on all sides by other qualities, to which it belongs and without which it could not subsist. For us, however, to lift certain sections out from the rest of the world and to consider them by themselves, is a necessity. Our eye can take hold of only single colors, one after another, out of a totality of many colors, our understanding, of only single concepts out of a coherent system of concepts. This separating off is a subjective act, and it is due to the fact that man is not identical with the world process, but is a being among other beings.
Now all depends on our defining how the being of man is related to other beings. This definition must be distinguished from merely becoming conscious of ourselves. This latter depends on the act of perceiving, just as does our becoming conscious of anything else. Self-perception shows me a number of qualities which I comprise in the unity of my personality in the same way as I comprise the qualities yellow, metallic, hard, etc., in the unity “gold.” Self-perception does not take me beyond the sphere of what belongs to myself. This perceiving myself is to be distinguished from defining myself by means of thinking. Just as I insert a separate perception of the external world into the connection of things by means of thinking, so do I insert the perceptions derived from myself into the world process by means of thinking. When I perceive myself, then I see myself as enclosed within certain limits, but my thinking has nothing to do with these limits. In this sense I am a twofold being. I am enclosed within the sphere which I perceive as that of my personality, but I am also the bearer of an activity which, from a higher sphere, determines my limited existence. Our thinking is not individual like our sensing and feeling. It is universal. It receives an individual stamp in each separate human being only because it becomes related to his individual feelings and sensations. Through these particular colorings of the universal thinking, single persons differ from one another. A triangle has only one single concept. For the content of this concept it is quite immaterial whether the human bearer of consciousness who grasps it is A or B. But it will be grasped by each of the two bearers of consciousness in an individual way.
This thought conflicts with a common prejudice which is very hard to overcome. Those who have this prejudice cannot reach the insight that the concept of triangle which my head grasps is the same concept as that which my neighbor's head grasps. The naive man considers himself to be the maker of his concepts. He therefore believes that each person has his own concepts. It is a fundamental requirement of philosophic thinking to overcome this prejudice. The one undivided concept, triangle, does not become a multiplicity because it is thought by many. For the thinking of the many is itself a unity.
In thinking, we are given that element which embraces our particular individuality and makes it one with the cosmos. In that we sense and feel (and also perceive), we are single entities; in that we think, we are the All-One Being that pervades everything. This is the deeper foundation of our twofold being: We see within us a simply absolute force come into existence, a force which is universal, but we learn to know it, not as it issues from the center of the world, but at a point of the periphery. Were the former the case, as soon as we came to be conscious, we should know the whole world riddle. But since we stand at a point on the periphery and find that our own existence is confined within definite limits, we must learn to know the region which lies beyond our own being with the help of thinking, which penetrates into us out of the general world existence.
Through the fact that the thinking in us reaches out beyond our separate existence and relates itself to the general world existence, there arises in us the urge for knowledge. Beings without thinking do not have this urge. When other things confront them, this gives rise to no questioning within them. These other things remain external to such beings. But the concept rises up within thinking beings when they confront external things. It is that part of things which we receive not from outside, but from within. It is for knowledge to bring about the agreement, the union of the two elements, the inner and the outer.
The perception therefore is not something finished, not something self-contained, but one side of the total reality. The other side is the concept. The act of knowledge is the synthesis of perception and concept. Only perception and concept together constitute the whole thing.
The above explanations give proof that it is meaningless to seek for any common factor in the separate entities of the world, other than the ideal content to be found in thinking. All efforts must fail which seek to find any other world unity than this internally coherent ideal content which we gain by thinking consideration of our perceptions. Neither a humanly personal God, nor force, nor matter, nor idea-less will (Schopenhauer), is acceptable as the universal world unity. All these entities belong only to a limited sphere of our observation. Humanly limited personality we perceive only in man, force and matter in external things. As regards the will, it can be considered only as the expression of the activity of our finite personality. Schopenhauer  wants to avoid making “abstract” thinking the bearer of the world unity, and instead seeks something which seems to him to be immediate reality. This philosopher believes we can never approach the world so long as we regard it as an external world.
“In fact, the meaning sought for in the world that confronts me solely as my representation, or the transition from it, as mere representation of the cognizing subject, to whatever it may be besides this, could never be found if the investigator himself were nothing more than the pure cognizing subject (a winged cherub without a body). But he himself is rooted in that world, he finds himself in it as an individual; this means that his knowledge, which is the necessary bearer of the whole world as representation, is yet always given through the medium of a body, whose affections are, as we have shown, the starting point from which the intellect forms a view of that world. For the pure cognizing subject as such, this body is a representation like every other representation, an object among objects; in this respect its movements and actions are known to him in no other way than the changes in all other objects which he can contemplate, and would be just as strange and incomprehensible to him if their meaning were not revealed to him in an entirely different way. ... For the subject of cognition, who appears as an individual through his identity with the body, this body is given in two entirely different ways: It is given as a representation for intelligent consideration, as object among objects and subjected to their laws; but also, at the same time, in quite a different way, namely, as that which is directly known to everyone, and which is called will. Every true act of his will is also at once and unfailingly a movement of his body: he cannot will the act without perceiving at the same time that it appears as a movement of the body. The act of will and the action of the body are not two different conditions objectively recognized, connected by the bond of causality; they do not stand in the relation of cause and effect; they are one and the same, but are given in two entirely different ways: once quite directly, and once again for the intelligence that considers it.” 
By these arguments Schopenhauer believes himself entitled to see in the human body the “objectivity” of the will. In his opinion one feels in the actions of the body a direct reality, the thing-in-itself in the concrete. The objection to these arguments is that the actions of our body come to our consciousness only through self-perceptions, and that, as such, they are in no way superior to other perceptions. If we want to learn to know their nature, we can do so only by thinking investigation, that is, by fitting them into the ideal system of our concepts and ideas.
Rooted most deeply in the naive consciousness of mankind is the opinion: Thinking is abstract, empty of all concrete content. At most it can give an “ideal” mirror-picture of the world, but nothing of the world itself. To judge like this is never to have become clear about what perception without the concept, is. Let us look at this realm of mere perceptions: it appears as a mere juxtaposition in space, a mere succession in time, an aggregate of disconnected entities. None of the things which come and go on the stage of perception have any direct, perceptible connection with any others. From this aspect, the world is a multiplicity of objects of equal value. None plays any greater part in the hustle and bustle of the world than any other. If it is to become clear to us that this or that fact has greater significance than another, we must consult our thinking. Without the functioning of thinking, the rudimentary organ of an animal which has no significance in its life appears to us as equal in value to the most important limb. The separate facts appear in their own significance, as well as in their significance for the rest of the world only when thinking spins its threads from one entity to another. This activity of thinking is one filled with content. For it is only through a quite definite, concrete content that I can know why the snail belongs to a lower level of organization than the lion. The mere sight, the perception, gives me no content which can inform me about the degree of perfection of an organization.
Thinking brings this content to the perception from man's world of concepts and ideas. In contrast to the content of perception given to us from outside, the content of thought shines forth in the inner being of man. The manner in which the content of thought first appears, we will call intuition. Intuition is for thinking what observation is for perception. Intuition and observation are the sources of our knowledge. An observed object or event is foreign to us as long as we do not have in our inner being the corresponding intuition which completes for us that part of reality which is missing in the perception. To someone who lacks the ability to find intuitions corresponding to things, the full reality remains inaccessible. Just as the color-blind sees only differences of brightness without any color qualities, so the one who lacks intuition can observe only disconnected fragments of perceptions.
To explain a thing, to make it intelligible, means nothing other than to place it into the context from which it has been torn owing to the nature of our organization as described above. Something cut off from the world whole does not exist. Isolation in any form has only subjective validity for our organization. For us the world unity divides itself into above and below, before and after, cause and effect, object and representation, matter and force, object and subject, etc. What appears to our observation as single entities, combines, bit by bit, through the coherent, undivided world of our intuitions, and through thinking we again fit together into a unity everything we had divided through perceiving.
The enigmatic aspect of an object is due to its separate existence. But this separation is brought about by us and, within the world of concepts, can be canceled again.
Except through thinking and perceiving, nothing is given to us directly. The question now arises: What significance has perception according to our line of thought? We have, it is true, recognized that the proof which critical idealism brings forward for the subjective nature of perceptions, collapses, but the insight that the proof is wrong does not necessarily mean that what is asserted is incorrect. Critical idealism does not base its proof on the absolute nature of thinking, but relies on the fact that naive realism, when followed to its logical conclusion, contradicts itself. How does the matter stand when the absoluteness of thinking is recognized?
Let us assume that a certain perception, for example, red, appears in my consciousness. Continued consideration will show the perception to be connected with other perceptions, for example, a definite form, certain perceptions of temperature, and of touch. This combination I call an object of the sense world. I can now ask: Over and above the perceptions just mentioned, what else is there in that section of space where they appear? I shall find mechanical, chemical and other processes in that section of space. I now go further and investigate the processes I find on the way from the object to my sense organs. I can find movements in an elastic medium, and their nature has not the slightest thing in common with the original perception. I get the same result when I go on and investigate the further transmission between sense organs and brain. In each of these spheres I gather new perceptions, but the connecting medium permeating all these perceptions standing side by side in both space and time, is thinking. The air vibrations which carry sound are given me as perception, just as is the sound itself. Thinking alone links all these perceptions to one another, showing them in their mutual relationships. Beyond what is directly perceived, we cannot speak of anything except what can be recognized through the ideal connections of perceptions (that is, what can be discovered through thinking). That relationship between the perceptual object and the perceiving subject, which goes beyond what can be perceived, is therefore a purely ideal one, that is, it can be expressed only by means of concepts. Only if I could perceive how the perceptual object affects the perceiving subject, or, the other way round, if I could observe the building up of the perceptual pictures by the subject, would it be possible to speak as does modern physiology and the critical idealism based on it. This view confuses an ideal relation (that of the object to the subject) with a process which we could speak of only if it were possible to perceive it. The principle, “No color without a color-seeing eye,” is therefore not to be taken to mean that the eye produces the color, but only that an ideal relationship, recognizable by thinking, exists between the perception, color and the perception, eye. Empirical science will have to establish how the nature of the eye and the nature of colors are related to one another, that is, by what means the organ of sight transmits the perception of colors, etc. I can trace how one perception succeeds another and how one is related to others in space, and I can formulate this in conceptual terms, but I cannot perceive how a perception originates out of the non-perceptible. All attempts to seek any relations between perceptions other than thought relations must of necessity fail.
What, then, is a perception? When asked in general, this question is absurd. A perception always appears as a quite definite, concrete content. This content is directly given and is completely contained within the given. The only question one can ask concerning this given is, What is it apart from being a perception; that is, What is it for thinking? The question concerning the “what” of a perception, therefore, can refer only to the conceptual intuition which corresponds to it. Seen in this light, the question of the subjectivity of perceptions, in the sense of critical idealism, cannot be raised at all. Only what is perceived as belonging to the subject can be termed “subjective.” No real process, in a naive sense, can form a link between the subjective and the objective, that is, no process that can be perceived; this is possible only for thinking. For us, then, that is objective which, to perception, lies outside of the perceptual subject. My perceptual subject remains perceptible to me when the table which stands before me has disappeared from my field of observation. My observation of the table has caused in me a change which likewise remains. I retain the ability to reproduce a picture of the table later. This ability to produce a picture remains connected with me. Psychology describes this picture as a memory representation. However, it is the only thing which can correctly be called the representation of the table. For it corresponds to the perceptible change in me, caused through the presence of the table in my field of vision. And indeed, it is not a change in some “I-in-itself” standing behind the perceptual subject, but a change in the perceptible subject itself. A representation, then, is a subjective perception, in contrast to the objective perception which occurs when the object is present in the field of vision. The confusing of the former subjective with the latter objective perception leads to the misunderstanding of idealism: The world is my representation.
The next step must be to define the concept of representation more exactly. What we have so far described of it is not its concept; what we have described has only pointed the way to where in the perceptual field representations are to be found. The exact concept of representation will also then make it possible for us to gain a satisfactory explanation of the relationship between representation and object. This will also lead us over the border-line, where the relationship between the human subject and the object belonging to the world is brought down from the purely conceptual field of knowledge into concrete individual life. Once we know what to think of the world, it will also be easy to adapt ourselves to it. We can only be active with our full human forces when we know the objects belonging to the world to which we devote our activity.
Addition to the Revised Edition, (1918): The view I have characterized here can be regarded as one to which man is led at first, as if by a natural instinct, the moment he begins to reflect upon his relation to the world. He then finds himself caught in a thought formation which dissolves for him while he frames it. This thought formation is such that a purely theoretical refutation of it does not suffice. One has to live through it and experience it in order to recognize how far it leads one astray, and then to find the way out. It must be a feature of any discussion concerning man's relation to the world, not for the sake of refuting others whose view about this relation one believes to be wrong, but because one must oneself experience to what confusion every first reflection about such a relation can lead. One must gain that insight which will enable one to refute oneself with respect to such a first reflection. The above discussion is meant in this sense.
When one tries to work out a view about man's relation to the world, one becomes conscious of the fact that man himself creates this relation, at least in part, by forming representations about the things and events in the world. This draws his attention away from what is present outside in the world and directs it to his inner world, to his life of forming representations. He begins to say to himself: It is impossible for me to have a relationship to any thing or event unless a representation of it appears in me. From noticing this fact, it is but a step to the opinion: All that I experience is, after all, only my representation; I know about a world outside me only insofar as it is representation in me. With this opinion, man abandons the standpoint of naive reality which he has before he begins to reflect about his relation to the world. From the naive standpoint, he believes that he is dealing with real things. But reflection about his own being drives him away from this standpoint. This reflection does not allow him to turn his gaze toward a real world such as naive consciousness believes it confronts. This reflection turns his gaze only toward his representations; his representations slip in between his own being and that real world the naive standpoint believes in. Man no longer can look through the intervening world of representations to any such reality. He has to assume that he is blind to this reality. So the thought arises of a “thing-in-itself” which is inaccessible to knowledge. — As long as one considers only the relationship to the world into which man appears to enter through his life of forming representations, one cannot escape from this line of thought. But one cannot remain at the naive standpoint of reality except by artificially curbing the thirst for knowledge. The fact that in man the need is present for knowledge about his relation to the world indicates that the naive standpoint must be abandoned. If the naive standpoint gave us anything that could be acknowledged as truth, then we should not feel this need. — But one does not arrive at anything else that could be considered as truth if one merely abandons the naive standpoint, but retains — without noticing it — the kind of thought which it imposes upon us. This is the mistake that is made when it is said: I experience only my representations, and while I believe that I am dealing with reality, I am actually conscious only of my representations of reality; I must, therefore, assume that genuine reality, the “thing-in-itself,” exists only outside the boundary of my consciousness and that I know nothing of it directly, but that it somehow approaches me and influences me in such a way that my representations come about. To think in this way is only to add in thought, to the world before us, another world; but one must begin the whole thinking process over again with regard to this second world. For the unknown “thing-in-itself,” in its relation to man's being, is thought of in exactly the same way as is the known thing of the naive standpoint of reality. — One only escapes the confusion that arises in one's critical reflection concerning this standpoint when one notices that inside everything we can experience by means of perceiving, be it within ourselves or outside in the world, there is something which cannot succumb to the fate that a representation inserts itself between event and contemplating human being. And this something is thinking. With regard to thinking, man can remain at the naive standpoint of reality. If he does not do so, it is only because he has noticed that he has to abandon this standpoint in regard to other things, but overlooks the fact that this insight, which is true for other things, does not apply to thinking. When he notices this, he opens the portal to yet another insight, that in thinking and through thinking that must be acknowledged to which man appears to blind himself because he has to place between himself and the world the life of representations. — A critic highly esteemed by the author of this book has objected that this discussion of thinking remains at naive realism in regard to thinking, as it must if the real world and the world of representations are held to be one and the same. However, the author believes he has shown in just this discussion this fact: that an unprejudiced observation of thinking inevitably shows that “naive realism” is valid for thinking, and that naive realism, insofar as it is not valid for other things, is overcome through the recognition of the true nature of thinking.