§ 6.

Meanwhile for the present, in this first book we are considering everything merely as representation, as object for the subject. And our own body, which is the starting-point for each of us in the perception of the world, we consider, like all other real objects, merely from the side of knowableness, and accordingly it is for us only a representation. Now the consciousness of everyone, which is already opposed to the explanation of other objects as mere representations, is in even greater opposition when his own body is said to be mere representation. Thus it happens that to everyone the thing-in-itself is known immediately in so far as it appears as his own body, and only mediately in so far as it is objectified in the other objects of perception. But the course of our investigation renders necessary this abstraction, this one-sided method of consideration, this forcible separation of two things that essentially exist together. Therefore this reluctance must for the time being be suppressed, and set at rest by the expectation that the following considerations will make up for the one-sidedness of this one, towards a complete knowledge of the nature of the world.

Here, therefore, the body is for us immediate object, in other words, that representation which forms the starting-point of the subject’s knowledge, since it itself with its immediately known changes precedes the application of the law of causality, and thus furnishes this with the first data. The whole essence of matter consists, as we have shown, in its action. But there are cause and effect only for the understanding, which is nothing but the subjective correlative of these. The understanding, however, could never attain to application, if there were not something else from which it starts. Such a something is the mere sensation, the immediate consciousness of the changes of the body, by virtue of which this body is immediate object. Accordingly the possibility of knowing the world of perception is to be found in two conditions; the first is, if we express it objectively, the ability of bodies to act on one another, to bring about changes in one another. Without that universal property of all bodies no perception would be possible, even by means of the sensibility of animal bodies. If, however, we wish to express this same first condition subjectively , we say that the understanding first of all makes perception possible, for the law of causality, the possibility of effect and cause, springs only from the understanding, and is valid also for it alone; hence the world of perception exists only for it and through it. The second condition, however, is the sensibility of animal bodies, or the quality possessed by certain bodies of being directly objects of the subject. The mere changes sustained from without by the sense-organs through the impression specifically appropriate to them can themselves be called representations, in so far as such impressions stimulate neither pain nor pleasure, in other words, have no immediate significance for the will, and yet are perceived, i.e. exist only for knowledge. To this extent, therefore, I say that the body is immediately known, is immediate object. The conception of object, however, is not to be taken here in the fullest sense, for through this immediate knowledge of the body, which precedes the application of the understanding and is mere sensation, the body itself does not exist really as object, but first the bodies acting on it. For all knowledge of an object proper, in other words, of a representation of perception in space, exists only through and for the understanding, and thus not before, but only after, the application of the understanding. Therefore the body as object proper, in other words, as representation of perception in space, is first known indirectly, like all other objects, through the application of the law of causality to the action of one of its parts on another, as by the eye seeing the body, or the hand touching it. Consequently the form of our own body does not become known to us through mere ordinary feeling, but only through knowledge, only in the representation; in other words, only in the brain does our own body first present itself as an extended, articulate, organic thing. A person born blind receives this representation only gradually through data afforded him by touch. A blind man without hands would never get to know his form, or at most would infer and construct it gradually from the impression on him of other bodies. Therefore, if we call the body immediate object, we are to be understood as implying this restriction.

Moreover, it follows from what has been said that all animal bodies are immediate objects, in other words starting-points in the perception of the world for the subject that knows all, and, for this very reason, is never known. Knowledge, therefore, with movement consequent on motives conditioned by it, is the proper characteristic of animal life, just as movement consequent on stimuli is the characteristic of the plant. But that which is unorganized has no movement other than that produced by causes proper in the narrowest sense. I have discussed all this at length in the essay On the Principle of Sufficient Reason (second ed., § 20), in the Ethics (first essay, iii), and in my Vision and Colours (§ i), to which therefore I refer the reader.

It follows from what has been said that all animals, even the most imperfect, have understanding, for they all know objects, and this knowledge as motive determines their movements. The understanding is the same in all animals and in all men; everywhere it has the same simple form, that is to say, knowledge of causality, transition from effect to cause and from cause to effect, and nothing else. But the degree of its acuteness and the extent of its sphere of knowledge vary enormously, with many different gradations, from the lowest degree, which knows only the causal relation between the immediate object and indirect ones, and hence is just sufficient to perceive a cause as object in space by passing from the impression experienced by the body to the cause of this impression, up to the higher degrees of knowledge of the causal connexion among merely indirect objects. Such knowledge extends to the understanding of the most complicated concatenations of causes and effects in nature; for even this last degree of knowledge still belongs always to the understanding, not to the faculty of reason. The abstract concepts of reason can only serve to handle what is immediately understood, to fix and arrange this, but never to bring about understanding itself. Every force and law of nature, every case in which such forces and laws are manifested, must first be known immediately by the understanding, must be intuitively apprehended, before it can pass into reflected consciousness in abstracto for the faculty of reason. Hooke’s discovery of the law of gravitation, and the reference of so many important phenomena to this one law, were intuitive, immediate apprehension through the understanding, and this was also confirmed by Newton’s calculations. The same may be said also of Lavoisier’s discovery of acids and their important role in nature, and of Goethe’s discovery of the origin of physical colours. All these discoveries are nothing but a correct immediate return from the effect to the cause, which is at once followed by recognition of the identity of the natural force which manifests itself in all causes of the same kind. This complete insight is an expression, differing merely in degree, of the same single function of the understanding, by which an animal perceives as object in space the cause affecting its body. Therefore all those great discoveries are, just like perception and every manifestation of understanding, an immediate insight, and as such the work of an instant, an aperçu, a sudden idea. They are not the product of long chains of abstract reasoning ; these, on the contrary, serve to fix the immediate knowledge of the understanding for the faculty of reason by setting down such knowledge in the abstract concepts of such reason, in other words, to make it clear, to be in a position to point it out and explain it to others. That keenness of the understanding in apprehending the causal relations of objects indirectly known finds its application not only in natural science (all the discoveries of which are due to it), but also in practical life, where it is called good sense or prudence. But in its first application it is better called acuteness, penetration, sagacity. Strictly speaking, good sense or prudence signifies exclusively understanding in the service of the will. However, the boundaries of these concepts are never to be drawn sharply, for it is always one and the same function of the same understanding at work in every animal when perceiving objects in space. In its greatest keenness, it accurately investigates in natural phenomena the unknown cause from the given effect, and thus provides the faculty of reason with the material for conceiving general rules as laws of nature. Again, it invents complicated and ingenious machines by applying known causes to intended effects. Or, applied to motivation, it sees through and frustrates subtle intrigues and machinations, or suitably arranges even the motives and the men susceptible to each of them, sets them in motion at will as machines are set in motion by levers and wheels, and directs them to its ends. Want of understanding is called in the proper sense stupidity, and it is just dulness in applying the law of causality, incapacity for the immediate apprehension of the concatenations of cause and effect, of motive and action. A stupid person has no insight into the connexion of natural phenomena, either when they appear of their own accord or when they are intentionally controlled, in other words made to serve machines. For this reason, he readily believes in magic and miracles. A stupid man does not notice that different persons, apparently independent of one another, are in fact acting together by agreement; he is therefore easily mystified and puzzled. He does not observe the concealed motives of proffered advice, expressed opinions, and so on. But it is invariably only one thing that he lacks, namely keenness, rapidity, ease in applying the law of causality, in other words, power of the understanding. The greatest and, in this respect, the most instructive example of stupidity that I ever came across was that of a totally imbecile boy of about eleven years of age in an asylum. He certainly had the faculty of reason, for he spoke and comprehended, but in understanding he was inferior to many animals. When I came, he noticed an eye-glass which I was wearing round my neck, and in which the windows of the room and the tops of the trees beyond them were reflected. Every time he was greatly astonished and delighted with this, and was never tired of looking at it with surprise. This was because he did not understand this absolutely direct causation of reflection.

As the degree of acuteness of understanding varies a great deal as between men, so does it vary even more as between the different species of animals. In all species, even those nearest to the plant, there exists as much understanding as is sufficient for passing from the effect in the immediate object to the mediate object as cause, and hence for perception, for the apprehension of an object. For it is just this that makes them animals, since it gives them the possibility of movement consequent on motives, and thus of seeking, or at any rate of grasping, nourishment. Plants, on the other hand, have only movement consequent on stimuli, the direct influence of which they must await or else droop; they cannot go after them or grasp them. In the most accomplished animals we marvel at their great sagacity, such as the dog, the elephant, the monkey, or the fox, whose cleverness has been described by Buffon in so masterly a way. In these most sagacious animals we can determine pretty accurately what the understanding is capable of without the aid of reason, that is to say, without the aid of abstract knowledge in concepts. We cannot find this out in ourselves, because in us understanding and the faculty of reason are always mutually supported. Therefore we find that the manifestations of understanding in animals are sometimes above our expectation, sometimes below it. On the one hand, we are surprised at the sagacity of that elephant which, after crossing many bridges on his journey through Europe, once refused to go on one, over which he saw the rest of the party of men and horses crossing as usual, because it seemed to him too lightly built for his weight. On the other hand, we wonder that the intelligent orang-utans, warming themselves at a fire they have found, do not keep it going by replenishing it with wood; a proof that this requires a deliberation that does not come about without abstract concepts. It is quite certain that the knowledge of cause and effect, as the universal form of the understanding, is a priori inherent in animals, because for them as for us it is the preliminary condition of all knowledge of the external world through perception. If we still want a special proof of this, let us observe, for example, how even a quite young dog does not venture to jump from the table, however much he wants to, because he foresees the effect of the weight of his body, without, however, knowing this particular case from experience. Meanwhile, in judging the understanding of animals, we must guard against ascribing to it a manifestation of instinct, a quality that is entirely different from it as well as from the faculty of reason; yet it often acts very analogously to the combined activity of these two. The discussion of this, however, does not belong here, but will find its place in the second book, when we are considering the harmony or so-called teleology of nature. The twenty-seventh chapter of the supplementary volume is expressly devoted to it.

Lack of understanding was called stupidity; deficiency in the application of the faculty of reason to what is practical we shall later recognize as foolishness; deficiency in power of judgement as silliness; finally, partial or even complete lack of memory as madness. But we shall consider each of these in its proper place. That which is correctly known through the faculty of reason is truth, namely an abstract judgement with sufficient ground or reason (essay On the Principle of Sufficient Reason, § 29 seqq.) ; that which is correctly known by understanding is reality, namely correctly passing from the effect in the immediate object to its cause. Error is opposed to truth as deception of reason; illusion is opposed to reality as deception of understanding. The detailed discussion of all this is to be found in the first chapter of my essay On Vision and Colours. Illusion comes about when one and the same effect can be brought to pass by two entirely different causes, one of which operates very frequently, the other very rarely. The understanding, having no datum for determining which cause operates in a given case, since the effect is identical, always presupposes the ordinary cause, and because the activity of the understanding is not reflective and discursive, but direct and immediate, such false cause stands before us as perceived object, which is just the false illusion. I have shown, in the essay referred to, how in this way double sight and double touch occur, when the organs of sense are brought into an unusual position, and I have thus given an irrefutable proof that perception exists only through the understanding and for the understanding. Examples of such deception of understanding, or illusion, are the stick that seems broken when dipped in water, the images of spherical mirrors appearing with convex surface somewhat behind them, with concave surface well before them. To this class of examples also belongs the apparently greater extension of the moon at the horizon than at the zenith. This is not optical, for, as the micrometer proves, the eye apprehends the moon at the zenith at an even greater angle of vision than at the horizon. It is the understanding that assumes the cause of the feebler brightness of the moon and of all stars at the horizon to be their greater distance, treating them like earthly objects in accordance with atmospheric perspective. Therefore it regards the moon at the horizon as very much larger than at the zenith, and at the same time also considers the vault of heaven to be more extended, and hence flattened out, at the horizon. The same estimation, falsely applied according to atmospheric perspective, leads us to suppose that very high mountains, whose summits are visible to us only in pure transparent air, are nearer than they really are, to the detriment of their height; as for example, Mont Blanc seen from Salenche. All such deceptive illusions stand before us in immediate perception which cannot be removed by any arguments of reason. Such arguments can prevent merely error, that is to say, a judgement without sufficient ground or reason, by forming an opposite judgement that is true; for instance, knowing in the abstract that the cause of the weaker light of the moon and stars in the case cited is not the greater distance, but the cloudier atmosphere at the horizon. But the illusion remains unshakable in all the cases mentioned, in spite of all abstract knowledge; for the understanding is completely and totally different from the faculty of reason, a cognitive faculty that has been added to man alone; and indeed the understanding is in itself irrational, even in man. Reason can always only know; perception remains free from its influence, and belongs to the understanding alone.