The Rudolf Steiner Archive

4. The World as Perception

[ 1 ] Thinking gives rise to concepts and ideas. What a concept is cannot be expressed in words. Words can only make a person aware that he has concepts. When someone sees a tree, their thinking reacts to their observation; an ideal counterpart is added to the object, and they regard the object and the ideal counterpart as belonging together. When the object disappears from their field of vision, only the ideal counterpart remains. The latter is the concept of the object. The more our experience expands, the greater the sum of our concepts becomes. However, the concepts do not stand in isolation. They coalesce into a systematic whole. The concept “organism,” for example, connects to the others: “systematic development, growth.” Other concepts formed from individual things merge completely into one. All the concepts I form of lions merge into the general concept “lion.” In this way, the individual concepts combine into a closed conceptual system in which each has its own specific place. Ideas are not qualitatively different from concepts. They are merely more content-rich, more saturated, and more comprehensive concepts. I must place particular emphasis on noting here that I have designated thinking as my starting point, and not concepts and ideas, which are only gained through thinking. These already presuppose thinking. Therefore, what I have said regarding the self-contained, undetermined nature of thought cannot simply be applied to concepts. (I note this explicitly here because this is where my difference with Hegel lies. He posits the concept as the first and original.)

[ 2 ] The concept cannot be derived from observation. This is evident from the fact that a growing person only slowly and gradually forms concepts about the objects that surround them. The concepts are added to the observation.

[ 3 ] Herbert Spencer, a widely read contemporary philosopher, describes the mental process we undergo in response to observation as follows:

[ 4 ] “If, on a September day, we are walking through the fields and hear a sound a few steps ahead of us, and see the grass moving at the edge of the ditch from which it seemed to come, we will probably head toward that spot to find out what caused the sound and the movement. As we approach, a partridge flutters into the ditch, and our curiosity is satisfied: we have what we call an explanation of the phenomena. This explanation, mind you, boils down to the following: because we have experienced countless times in life that a disturbance of the quiet state of small bodies is accompanied by the movement of other bodies situated between them, and because we have therefore generalized the relationships between such disturbances and such movements, we consider this particular disturbance explained as soon as we find that it presents an example of precisely this relationship.” On closer inspection, the matter presents itself quite differently than it is described here. When I hear a sound, I first seek the concept for this observation. It is this concept that points me beyond the sound. Those who do not think further simply hear the sound and are satisfied with that. Through my reflection, however, it becomes clear to me that I must understand a sound as an effect. Thus, only when I connect the concept of effect with the perception of the sound am I prompted to go beyond the individual observation and search for the cause. The concept of effect gives rise to that of cause, and I then search for the causative object, which I find in the form of the partridge. However, I can never arrive at these concepts—cause and effect—through mere observation, no matter how many instances they may cover. Observation challenges thought, and it is thought alone that shows me the way to link one individual experience to another.

[ 5 ] If one demands that a “strictly objective science” derive its content solely from observation, one must at the same time demand that it renounce all thinking. For thinking, by its very nature, goes beyond what is observed.

[ 6 ] Now is the time to move from thought to the thinking being. For it is through this that thought is linked to observation. Human consciousness is the arena where concept and observation meet and where they are linked together. This, however, is also what characterizes this (human) consciousness. It is the mediator between thought and observation. Insofar as a person observes an object, it appears to him as given; insofar as he thinks, he appears to himself as active. He regards the object as object, himself as the thinking subject. Because he directs his thinking toward observation, he has consciousness of the objects; because he directs his thinking toward himself, he has consciousness of himself or self-consciousness. Human consciousness must necessarily be self-consciousness at the same time, because it is thinking consciousness. For when thinking directs its gaze toward its own activity, it has its very own essence—that is, its subject—as its object.

[ 7 ] However, we must not overlook the fact that it is only through thinking that we can define ourselves as subjects and set ourselves apart from objects. Therefore, thinking must never be understood as a merely subjective activity. Thinking is beyond subject and object. It forms these two concepts just as it forms all others. Thus, when we, as thinking subjects, apply a concept to an object, we must not regard this relationship as something merely subjective. It is not the subject that brings about the relationship, but thinking. The subject does not think because it is a subject; rather, it appears to itself as a subject because it is capable of thinking. The activity that human beings exercise as thinking beings is therefore not merely subjective, but one that is neither subjective nor objective, one that transcends these two concepts. I must never say that my individual subject thinks; rather, it lives by the grace of thought itself. Thought is thus an element that leads me beyond my self and connects me with objects. But at the same time, it separates me from them by setting me against them as a subject.

[ 8 ] This is the basis of the dual nature of human beings: they think, thereby encompassing themselves and the rest of the world; but at the same time, through thinking, they must define themselves as individuals standing in opposition to things.

[ 9 ] The next step is to ask ourselves: How does the other element—which we have so far referred to merely as an object of observation, and which encounters thought within consciousness—enter into the latter?

[ 10 ] To answer this question, we must eliminate from our field of observation everything that has already been introduced into it by thought. For the content of our consciousness is always already interwoven with concepts in the most varied ways.

[ 11 ] We must create a mental image of a being with fully developed human intelligence arising out of nothing and encountering the world. What it would perceive there, before it begins to think, is the pure content of observation. The world would then present to this being only the mere, disjointed aggregate of objects of sensation: colors, sounds, pressure, heat, tastes, and smells; then feelings of pleasure and displeasure. This aggregate is the content of pure, thoughtless observation. Opposed to this is thought, which is ready to unfold its activity when a point of entry is found. Experience soon teaches that such a point is found. Thought is capable of drawing connections from one element of observation to another. It links certain concepts to these elements and thereby relates them to one another. We have already seen above how a sound we encounter is linked to another observation by our designating the former as the effect of the latter.

[ 12 ] If we now recall that the act of thinking is by no means to be understood as a purely subjective one, we will not be tempted to believe that such relationships, which are established through thinking, have merely subjective validity.

[ 13 ] The task now is to use reason to identify the relationship between the immediately given observational content described above and our conscious subject.

[ 14 ] Given the variability in language usage, it seems necessary for me to clarify with my reader the meaning of a word that I must use in what follows. I shall call the immediate objects of sensation that I have mentioned above perceptions, insofar as the conscious subject takes note of them through observation. Thus, I use this term not to denote the process of observation, but rather the object of this observation.

[ 15 ] I do not choose the term sensation because it has a specific meaning in physiology that is narrower than my concept of perception. I can certainly describe a feeling within myself as perception, but not as sensation in the physiological sense. I also become aware of my feelings through the fact that they become perception for me. And the way in which we gain knowledge of our thinking through observation is such that we can also call thinking, in its first appearance to our consciousness, perception.

[ 16 ] The naive person regards his perceptions, in the sense in which they immediately appear to him, as things that have an existence entirely independent of him. When he sees a tree, he initially believes that it stands in the form he sees, with the colors of its parts, etc., at the place where his gaze is directed. When the same person sees the sun appear in the morning as a disk on the horizon and follows the course of this disk, he is of the opinion that all of this exists and proceeds in this way (in itself), just as he observes it. He holds fast to this belief until he encounters other perceptions that contradict it. The child, who has no experience of distances yet, reaches for the moon and only corrects what it initially took to be real when a second perception contradicts the first. Every expansion of the scope of my perceptions compels me to correct my picture of the world. This is evident in daily life as well as in the spiritual development of humanity. The picture that the ancients formed of the relationship between the Earth and the Sun and the other celestial bodies had to be replaced by a different one by Copernicus, because it did not agree with perceptions that were previously unknown. When Dr. Franz operated on a man born blind, the latter said that before his operation, he had formed a completely different picture of the size of objects through the perceptions of his sense of touch. He had to correct his tactile perceptions through his visual perceptions.

[ 17 ] Why is it that we are forced to constantly correct our observations?

[ 18 ] A simple consideration provides the answer to this question. When I stand at one end of an avenue, the trees at the other end—which is farther away from me—appear smaller and closer together than they do where I am standing. My perceptual image changes when I change the location from which I make my observations. It is therefore, in the form in which it presents itself to me, dependent on a condition that does not depend on the object, but rather on me, the observer. It makes no difference to an avenue where I stand. But the image I receive of it depends essentially on that. Likewise, it makes no difference to the sun and the planetary system that people are looking at them from Earth. The perceptual image that presents itself to them, however, is determined by their location. This dependence of the perceptual image on our place of observation is the one that is easiest to grasp. The matter becomes more difficult when we come to understand the dependence of our perceptual world on our physical and mental constitution. The physicist shows us that within the space in which we hear a sound, vibrations of the air take place, and that the body in which we seek the source of the sound also exhibits a vibrating movement of its parts. We perceive this movement as sound only if we have a normally functioning ear. Without such an ear, the whole world would remain eternally silent to us. Physiology teaches us that there are people who perceive nothing of the magnificent splendor of colors that surrounds us. Their perceptual image consists only of shades of light and dark. Others perceive only a certain color, for example red, not at all. Their worldview lacks this color tone, and it is therefore indeed different from that of the average person. I would call the dependence of my perceptual image on my vantage point a mathematical one, and that on my constitution a qualitative one. The former determines the proportions and mutual distances of my perceptions, the latter their quality. That I see a red surface as red—this qualitative determination—depends on the constitution of my eye.

[ 19 ] My perceptual images are, therefore, initially subjective. The realization of the subjective nature of our perceptions can easily lead to doubts as to whether anything objective underlies them at all. If we know that a perception—for example, of the color red or a certain tone—is not possible without a specific configuration of our organism, one may come to believe that it has no existence apart from our subjective organism, that it has no mode of existence without the act of perception of which it is the object. This view found a classic proponent in George Berkeley, who believed that from the moment a person becomes aware of the importance of the subject for perception, they can no longer believe in a world that exists without the conscious mind. He says: “Some truths are so obvious and so self-evident that one need only open one’s eyes to see them. I consider the important proposition that the entire host in heaven and everything that belongs to the earth—in a word, all the bodies that make up the mighty structure of the world— have no subsistence outside the mind, that their being consists in their being perceived—or recognized—that consequently, as long as they are not actually perceived by me or exist in my consciousness or that of another created mind, they either have no existence at all or exist in the consciousness of an eternal mind.” For this view, nothing remains of perception if one disregards the act of being perceived. There is no color if none is seen, no sound if none is heard. Just as little as color and sound do, extension, shape, and motion exist outside the act of perception. We see nowhere mere extension or form, but always these linked with color or other properties that are indisputably dependent on our subjectivity. If the latter disappear with our perception, then this must also be the case for the former, which are bound to them.

[ 20 ] The objection that, even if figure, color, tone, etc., have no existence other than that within the act of perception, there must still be things that exist without consciousness and to which the conscious perceptual images are similar, is met by the view described above with the statement: a color can only be similar to a color, a figure similar to a figure. Our perceptions can only be similar to our perceptions, but to no other things whatsoever. Even what we call an object is nothing other than a group of perceptions connected in a certain way. If I remove from a table its shape, extension, color, etc.—in short, everything that is merely my perception—nothing remains. This view, taken to its logical conclusion, leads to the assertion: The objects of my perceptions exist only through me, and indeed only insofar as and as long as I perceive them; they disappear with perception and have no meaning without it. Apart from my perceptions, however, I know of no objects and cannot know of any.

[ 21 ] There is no objection to this claim as long as I merely consider, in general terms, the fact that perception is influenced by the organization of my subject. The situation would be fundamentally different, however, if we were able to specify what role our perception plays in the formation of a perception. We would then know what happens to the perception during the act of perceiving, and could also determine what must already be present in it before it is perceived.

[ 22 ] This shifts our focus from the object of perception to the subject of perception. I do not merely perceive other things; I also perceive myself. The perception of myself initially consists in the fact that I am the enduring element in contrast to the constantly coming and going images of perception. The perception of the self can always occur in my consciousness while I am having other perceptions. When I am immersed in the perception of a given object, I am initially conscious only of that object. The perception of my self can then join this. I am now not merely conscious of the object, but also of my personality, which stands opposite the object and observes it. I do not merely see a tree, but I also know that it is I who sees it. I also recognize that something is happening within me while I observe the tree. When the tree disappears from my field of vision, a residue of this process remains in my consciousness: an image of the tree. This image has become connected with my self during my observation. My self has been enriched; its content has incorporated a new element. I call this element my mental image of the tree. I would never be in a position to speak of mental images if I did not experience them in the perception of my self. Perceptions would come and go; I would let them pass by. Only because I perceive my self and notice that with every perception its content also changes, am I compelled to relate the observation of the object to the change in my own state and to speak of my mental image.

[ 23 ] I perceive this mental image in myself in the same way that I perceive color, sound, etc., in other objects. I can now also make the distinction that I call these other objects, which stand opposite me, the external world, while I designate the content of my self-perception as the inner world. The misunderstanding of the relationship between mental image and object has led to the greatest misunderstandings in modern philosophy. The perception of a change within us—the modification that my self undergoes—has been thrust into the foreground, while the object causing this modification has been entirely lost sight of. It has been said: we do not perceive objects, but only our mental images. I am supposed to know nothing of the table in itself, which is the object of my observation, but only of the change that takes place within myself while I perceive the table. This view must not be confused with the Berkeleyan one mentioned earlier. Berkeley asserts the subjective nature of the content of my perception, but he does not say that I can know only my mental images. He limits my knowledge to my mental images because he believes that there are no objects outside of the mind. What I regard as a table ceases to exist in Berkeley’s sense as soon as I no longer direct my gaze toward it. Therefore, Berkeley posits that my perceptions arise directly through the power of God. I see a table because God evokes this perception within me. Berkeley therefore recognizes no real beings other than God and human minds. What we call the world exists only within the minds. What the naive person calls the external world, physical nature, does not exist for Berkeley. This view is contrasted by the now dominant Kantian one, which does not limit our knowledge of the world to our mental images because it is convinced that there can be no things outside these mental images, but because it believes us to be organized in such a way that we can only experience the changes in our own selves, not the things in themselves that cause these changes. It concludes from the fact that I know only my mental images, not that there is no existence independent of these mental images, but only that the subject cannot immediately apprehend such an existence within itself, cannot imagine, conceive, think, or recognize it—and perhaps cannot even fail to recognize it—other than through the “medium of its subjective thoughts” (O. Liebmann, On the Analysis of Reality, p. 28). This view believes it is stating something absolutely certain, something that is immediately self-evident without any proof. “The first fundamental proposition that the philosopher must bring to clear consciousness consists in the realization that our knowledge initially extends to nothing more than our mental images. Our mental images are the only thing we experience directly; and precisely because we experience them directly, even the most radical doubt cannot rob us of our knowledge of them. In contrast, knowledge that goes beyond our mental images—I am using this term here in the broadest sense, so that all mental activity falls under it—is not protected from doubt. “Therefore,” Volkelt begins his book on “Immanuel Kant’s Theory of Knowledge>, “at the outset of philosophical inquiry, all knowledge extending beyond mental images must be explicitly presented as subject to doubt.” What is presented here as if it were an immediate and self-evident truth is, however, in reality the result of a mental operation that proceeds as follows: The naive person believes that objects, just as he perceives them, also exist outside his consciousness. Physics, physiology, and psychology, however, seem to teach that our constitution is necessary for our perceptions, that we can consequently know nothing other than what our constitution conveys to us about things. Our perceptions are thus modifications of our organism, not things in themselves. The line of thought indicated here has in fact been characterized by Eduard von Hartmann as the one that must lead to the conviction that we can have direct knowledge only of our mental images (compare his “Grundproblem der Erkenntnistheorie,” pp. 16–40). Because we find vibrations of bodies and air outside our organism that present themselves to us as sound, it is concluded that what we call sound is nothing more than a subjective reaction of our organism to those movements in the external world. In the same way, it is held that color and heat are merely modifications of our organism. Specifically, it is believed that these two types of perception are evoked in us by the effect of processes in the external world that are entirely distinct from what constitutes the experience of heat or the experience of color. When such processes stimulate the skin nerves of my body, I have the subjective perception of heat; when such processes affect the optic nerve, I perceive light and color. Light, color, and heat are thus what my sensory nerves respond with to the external stimulus. Nor does the sense of touch provide me with the objects of the external world, but only with my own states. In the sense of modern physics, one might think, for example, that bodies consist of infinitely small parts, molecules, and that these molecules do not immediately adjoin one another, but are separated by certain distances. There is thus empty space between them. Through this space, they interact with one another by means of attractive and repulsive forces. When I bring my hand close to a body, the molecules of my hand do not touch those of the body directly at all, but a certain distance remains between the body and the hand, and what I perceive as the body’s resistance is nothing more than the effect of the repulsive force that its molecules exert on my hand. I am entirely outside the body and perceive only its effect on my organism.

[ 24 ] Complementing these considerations is the theory of so-called specific sensory energies, which J. Müller (1801–1858) proposed. It holds that each sense has the characteristic of responding to all external stimuli only in a specific way. When an effect is exerted on the optic nerve, light perception arises, regardless of whether the stimulation is caused by what we call light, or whether mechanical pressure or an electric current acts on the nerve. On the other hand, the same external stimuli evoke different perceptions in different senses. It seems to follow from this that our senses can convey only what takes place within them, but nothing from the external world. They determine perceptions according to their nature.

[ 25 ] Physiology shows that we cannot claim to have direct knowledge of what objects cause in our sense organs. By observing the processes within our own bodies, the physiologist finds that the effects of external movement are already altered in the most diverse ways within the sense organs. We see this most clearly in the eye and the ear. Both are highly complex organs that significantly alter the external stimulus before transmitting it to the corresponding nerve. From the peripheral end of the nerve, the already altered stimulus is then transmitted further to the brain. Only here must the central organs be stimulated again. From this, it is concluded that the external process has undergone a series of transformations before it reaches consciousness. What takes place in the brain is connected to the external process through so many intermediate processes that any resemblance to the latter can no longer be conceived. What the brain ultimately conveys to the soul are neither external processes nor processes in the sensory organs, but only those within the brain. Yet even the latter are not yet directly perceived by the soul. What we ultimately have in consciousness are not brain processes at all, but sensations. My sensation of red bears no resemblance whatsoever to the process that takes place in the brain when I perceive red. The latter only reappears as an effect in the soul and is caused solely by the brain process. That is why Hartmann (Grundproblem der Erkenntnistheorie, p. 37) says: “What the subject perceives are therefore always only modifications of its own mental states and nothing else.” When I have these sensations, however, they are still far from being grouped into what I perceive as things. After all, only individual sensations can be conveyed to me through the brain. The sensations of hardness and softness are conveyed to me through touch, while colors and light sensations are conveyed through sight. Yet these are found united in one and the same object. This unification must therefore first be effected by the soul itself. That is to say, the soul assembles the individual sensations conveyed by the brain into bodies. My brain conveys to me the sensations of sight, touch, and hearing individually, and in very different ways, which the soul then assembles into the mental image of a trumpet. This final link (the mental image of the trumpet) in a process is what is given to my consciousness first and foremost. In it, there is nothing left of what lies outside of me and originally made an impression on my senses. The external object has been completely lost on its way to the brain and through the brain to the soul.

[ 26 ] It would be difficult to find a second body of thought in the history of human intellectual life that has been assembled with greater acumen and that, upon closer examination, does not fall apart. Let us take a closer look at how this comes about. One starts with what is given to naive consciousness, with the perceived object. Then one shows that everything found in this object would not be there for us if we had no senses. No eye: no color. Thus, color is not yet present in what acts upon the eye. It arises only through the interaction of the eye with the object. The object is therefore colorless. But color is not present in the eye either; for there is a chemical or physical process there that is first transmitted to the brain via the nerve, where it triggers another. This is still not the color. It is only brought about by the brain process in the soul. There it still does not enter my consciousness, but is only transferred outward to a body by the soul. It is in this that I finally believe I perceive it. We have completed a full cycle. We have become conscious of a colored body. That is the first step. Now the mental process begins. If I had no eyes, the body would be colorless to me. I cannot, therefore, locate the color within the body. I set out in search of it. I look for it in the eye: in vain; in the nerve: in vain; in the brain: just as in vain; in the soul: here I do find it, but not connected to the body. I find the colored body again only where I started. The circle is complete. I believe I recognize as a product of my soul what the naive person imagines to exist out there in space.

[ 27 ] As long as one stops there, everything seems perfectly fine. But the matter must be taken up again from the beginning. Up until now, I have been dealing with one thing: external perception, about which I, as a naive person, used to have a completely mistaken view. I used to believe that it had an objective existence just as I perceive it. Now I realize that it vanishes with my mental image, that it is merely a modification of my mental states. Do I still have any right at all to take it as my starting point in my reflections? Can I say that it affects my soul? From now on, I must treat the table—which I used to believe affects me and produces a mental image of itself within me—as a mental image itself. Consequently, however, my sense organs and the processes within them are also merely subjective. I have no right to speak of a real eye, but only of my mental image of the eye. The same applies to nerve conduction and brain processes, and no less so to the process within the soul itself through which things are to be constructed from the chaos of manifold sensations. If, assuming the correctness of the first train of thought, I go through the stages of my act of cognition once more, the latter reveals itself as a web of mental images that, as such, cannot interact with one another. I cannot say: my mental image of the object acts upon my mental image of the eye, and from this interaction the mental image of color arises. But I have no need to do so. For as soon as it becomes clear to me that my sense organs and their activities, my nervous and mental processes, can be given to me only through perception, the line of thought described above reveals itself in its complete impossibility. It is true: for me, there is no perception without the corresponding sense organ. But just as there is no sense organ without perception. I can move from my perception of the table to the eye that sees it, to the skin nerves that touch it; but what goes on in these, I can again only learn from perception. And there I soon notice that in the process taking place in the eye, there is not a trace of similarity to what I perceive as color. I cannot destroy my perception of color by pointing out the process in the eye that takes place there during this perception. Nor do I find the color again in the nerves and brain processes; I merely connect new perceptions within my organism with the first one, which the naive person locates outside his organism. I merely move from one perception to another.

[ 28 ] Furthermore, the entire line of reasoning contains a leap. I am able to trace the processes in my body all the way to the processes in my brain, even though my assumptions become increasingly hypothetical the closer I get to the brain’s central processes. The path of external observation ends with the processes in my brain, specifically with those I would perceive if I could examine the brain using physical, chemical, and other such tools and methods. The path of internal observation begins with sensation and extends to the construction of things from sensory material. The path of observation is interrupted at the transition from the brain process to sensation.

[ 29 ] The mode of thought described here, which, in contrast to the standpoint of naive consciousness—which it calls naive realism—defines itself as critical idealism, makes the mistake of characterizing one perception as a mental image, while accepting the other precisely in the same sense as the naive realism it purports to refute. It seeks to prove the representational character of perceptions by naively accepting the perceptions of one’s own organism as objectively valid facts, and on top of that fails to realize that it is confusing two fields of observation between which it cannot find a mediation.

[ 30 ] Critical idealism can refute naive realism only if it itself assumes, in a naive-realist manner, that its own organism exists objectively. The very moment it becomes aware of the complete similarity between the perceptions of its own organism and those assumed by naive realism to exist objectively, it can no longer rely on the former as a secure foundation. It would also have to regard its own subjective organization as a mere complex of ideas. But this would mean losing the possibility of conceiving the content of the perceived world as brought about by the mental organization. One would have to assume that the mental image of “color” is merely a modification of the mental image of “eye.” So-called critical idealism cannot be proven without borrowing from naive realism. The latter is refuted only by allowing its own premises to remain unchallenged in another domain.

[ 31 ] One thing is certain: critical idealism cannot be proven through investigations within the realm of perception, and thus perception cannot be stripped of its objective character.

[ 32 ] Even less, however, should the statement: «The perceived world is my mental image» be presented as self-evident and in need of no proof. Schopenhauer begins his magnum opus *The World as Will and Representation* with the words: «The world is my mental image: — this is the truth that applies to every living and cognizing being; although man alone can bring it into reflective, abstract consciousness: and if he truly does so, philosophical prudence has taken hold of him. It then becomes clear and certain to him that he knows neither a sun nor an earth; but always only an eye that sees a sun, a hand that feels an earth; that the world surrounding him exists only as a mental image, that is, entirely only in relation to something else, the preceding, which is himself. — If any truth can be stated a priori, it is this: for it is the statement of that form of all possible and conceivable experience which is more general than all others, than time, space, and causality: for all these already presuppose that very form... » The entire proposition fails due to the circumstance I have already cited above, namely that the eye and the hand are no less mental images than the sun and the earth. And one could, in the spirit of Schopenhauer and drawing on his mode of expression, counter his propositions as follows: My eye, which sees the sun, and my hand, which feels the earth, are my mental images just as much as the sun and the earth themselves. But it is immediately clear that in doing so I am negating the sentence. For only my real eye and my real hand could have the mental images of the sun and the earth as their modifications in themselves, but not my mental images of the eye and the hand. Yet critical idealism may speak only of these.

[ 33 ] Critical idealism is completely unsuited to forming a view of the relationship between perception and mental images. It cannot make the distinction, hinted at on page 67 and following, between what happens to perception during the act of perceiving and what must already be present in it before it is perceived. Therefore, a different approach must be taken.