Thus although individual dreams are distinguished from real life by the fact that they do not fit into that continuity which runs through the whole of experience, and the act of awaking brings this into consciousness, yet that very continuity of experience belongs to real life as its form, and the dream on its part can point to a similar continuity in itself. If, therefore, we consider the question from a point of view external to both, there is no distinct difference in their nature, and we are forced to concede to the poets that life is a long dream.
Let us turn back now from this quite independent empirical origin of the question of the reality of the outer world, to its speculative origin. We found that this consisted, first, in the false application of the principle of sufficient reason to the relation of subject and object; and secondly, in the confusion of its forms, inasmuch as the principle of sufficient reason of knowing was extended to a province in which the principle of sufficient reason of being is valid. But the question could hardly have occupied philosophers so constantly if it were entirely devoid of all real content, and if some true thought and meaning did not lie at its heart as its real source. Accordingly, we must assume that when the element of truth that lies at the bottom of the question first came into reflection and sought its expression, it became involved in these confused and meaningless forms and problems. This at least is my opinion, and I think that the true expression of that inmost meaning of the question, which it failed to find, is this:—What is this world of perception besides being my idea? Is that of which I am conscious only as idea, exactly like my own body, of which I am doubly conscious, in one aspect as idea, in another aspect as will? The fuller explanation of this question and its answer in the affirmative, will form the content of the second book, and its consequences will occupy the remaining portion of this work.
§ 6. For the present, however, in this first book we consider everything merely as idea, as object for the subject. And our own body, which is the starting-point for each of us in our perception of the world, we consider, like all other real objects, from the side of its knowableness, and in this regard it is simply an idea. Now the consciousness of every one is in general opposed to the explanation of objects as mere ideas, and more especially to the explanation of our bodies as such; for the thing in itself is known to each of us immediately in so far as it appears as our own body; but in so far as it objectifies itself in the other objects of perception, it is known only indirectly. But this abstraction, this one-sided treatment, this forcible separation of what is essentially and necessarily united, is only adopted to meet the demands of our argument; and therefore the disinclination to it must, in the meantime, be suppressed and silenced by the expectation that the subsequent treatment will correct the one-sidedness of the present one, and complete our knowledge of the nature of the world.
At present therefore the body is for us immediate object; that is to say, that idea which forms the starting-point of the subject's knowledge; because the body, with its immediately known changes, precedes the application of the law of causality, and thus supplies it with its first data. The whole nature of matter consists, as we have seen, in its causal action. But cause and effect exist only for the understanding, which is nothing but their subjective correlative. The understanding, however, could never come into operation if there were not something else from which it starts. This is simple sensation—the immediate consciousness of the changes of the body, by virtue of which it is immediate object. Thus the possibility of knowing the world of perception depends upon two conditions; the first, objectively expressed, is the power of material things to act upon each other, to produce changes in each other, without which common quality of all bodies no perception would be possible, even by means of the sensibility of the animal body. And if we wish to express this condition subjectively we say: The understanding first makes perception possible; for the law of causality, the possibility of effect and cause, springs only from the understanding, and is valid only for it, and therefore the world of perception exists only through and for it. The second condition is the sensibility of animal bodies, or the quality of being immediate objects of the subject which certain bodies possess. The mere modification which the organs of sense sustain from without through their specific affections, may here be called ideas, so far as these affections produce neither pain nor pleasure, that is, have no immediate significance for the will, and are yet perceived, exist therefore only for knowledge. Thus far, then, I say that the body is immediately known, is immediate object. But the conception of object is not to be taken here in its fullest sense, for through this immediate knowledge of the body, which precedes the operation of the understanding, and is mere sensation, our own body does not exist specifically as object, but first the material things which affect it: for all knowledge of an object proper, of an idea perceived in space, exists only through and for the understanding; therefore not before, but only subsequently to its operation. Therefore the body as object proper, that is, as an idea perceived 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 upon another, as, for example, when the eye sees the body or the hand touches it. Consequently the form of our body does not become known to us through mere feeling, but only through knowledge, only in idea; that is to say, only in the brain does our own body first come to appear as extended, articulate, organic. A man born blind receives this idea only little by little from the data afforded by touch. A blind man without hands could never come to know his own form; or at the most could infer and construct it little by little from the effects of other bodies upon him. If, then, we call the body an immediate object, we are to be understood with these reservations.
In other respects, then, according to what has been said, all animal bodies are immediate objects; that is, starting-points for the subject which always knows and therefore is never known in its perception of the world. Thus the distinctive characteristic of animal life is knowledge, with movement following on motives, which are determined by knowledge, just as movement following on stimuli is the distinctive characteristic of plant-life. Unorganised matter, however, has no movement except such as is produced by causes properly so called, using the term in its narrowest sense. All this I have thoroughly discussed in my essay on the principle of sufficient reason, § 20, in the “Ethics,” first essay, iii., and in my work on Sight and Colour, § 1, to which I therefore refer.
It follows from what has been said, that all animals, even the least developed, have understanding; for they all know objects, and this knowledge determines their movements as motive. Understanding is the same in all animals and in all men; it has everywhere the same simple form; knowledge of causality, transition from effect to cause, and from cause to effect, nothing more; but the degree of its acuteness, and the extension of the sphere of its knowledge varies enormously, with innumerable gradations from the lowest form, which is only conscious of the causal connection between the immediate object and objects affecting it—that is to say, perceives a cause as an object in space by passing to it from the affection which the body feels, to the higher grades of knowledge of the causal connection among objects known indirectly, which extends to the understanding of the most complicated system of cause and effect in nature. For even this high degree of knowledge is still the work of the understanding, not of the reason. The abstract concepts of the reason can only serve to take up the objective connections which are immediately known by the understanding, to make them permanent for thought, and to relate them to each other; but reason never gives us immediate knowledge. Every force and law of nature, every example of such forces and laws, must first be immediately known by the understanding, must be apprehended through perception before it can pass into abstract consciousness for reason. Hooke's discovery of the law of gravitation, and the reference of so many important phenomena to this one law, was the work of immediate apprehension by the understanding; and such also was the proof of Newton's calculations, and Lavoisier's discovery of acids and their important function in nature, and also Goethe's discovery of the origin of physical colours. All these discoveries are nothing more than a correct immediate passage from the effect to the cause, which is at once followed by the recognition of the ideality of the force of nature which expresses itself in all causes of the same