Sors de l'enfance, ami réveille toi!
—Jean Jacques Rousseau.
§ 1. “The world is my idea:”—this is a truth which holds good for everything that lives and knows, though man alone can bring it into reflective and abstract consciousness. If he really does this, he has attained to philosophical wisdom. It then becomes clear and certain to him that what he knows is not a sun and an earth, but only an eye that sees a sun, a hand that feels an earth; that the world which surrounds him is there only as idea, i.e., only in relation to something else, the consciousness, which is himself. If any truth can be asserted a priori, it is this: for it is the expression of the most general form of all possible and thinkable experience: a form which is more general than time, or space, or causality, for they all presuppose it; and each of these, which we have seen to be just so many modes of the principle of sufficient reason, is valid only for a particular class of ideas; whereas the antithesis of object and subject is the common form of all these classes, is that form under which alone any idea of whatever kind it may be, abstract or intuitive, pure or empirical, is possible and thinkable. No truth therefore is more certain, more independent of all others, and less in need of proof than this, that all that exists for knowledge, and therefore this whole world, is only object in relation to subject, perception of a perceiver, in a word, idea. This is obviously true of the past and the future, as well as of the present, of what is farthest off, as of what is near; for it is true of time and space themselves, in which alone these distinctions arise. All that in any way belongs or can belong to the world is inevitably thus conditioned through the subject, and exists only for the subject. The world is idea.
This truth is by no means new. It was implicitly involved in the sceptical reflections from which Descartes started. Berkeley, however, was the first who distinctly enunciated it, and by this he has rendered a permanent service to philosophy, even though the rest of his teaching should not endure. Kant's primary mistake was the neglect of this principle, as is shown in the appendix. How early again this truth was recognised by the wise men of India, appearing indeed as the fundamental tenet of the Vedânta philosophy ascribed to Vyasa, is pointed out by Sir William Jones in the last of his essays: “On the philosophy of the Asiatics” (Asiatic Researches, vol. iv. p. 164), where he says, “The fundamental tenet of the Vedanta school consisted not in denying the existence of matter, that is, of solidity, impenetrability, and extended figure (to deny which would be lunacy), but in correcting the popular notion of it, and in contending that it has no essence independent of mental perception; that existence and perceptibility are convertible terms.” These words adequately express the compatibility of empirical reality and transcendental ideality.
In this first book, then, we consider the world only from this side, only so far as it is idea. The inward reluctance with which any one accepts the world as merely his idea, warns him that this view of it, however true it may be, is nevertheless one-sided, adopted in consequence of some arbitrary abstraction. And yet it is a conception from which he can never free himself. The defectiveness of this view will be corrected in the next book by means of a truth which is not so immediately certain as that from which we start here; a truth at which we can arrive only by deeper research and more severe abstraction, by the separation of what is different and the union of what is identical. This truth, which must be very serious and impressive if not awful to every one, is that a man can also say and must say, “the world is my will.”
In this book, however, we must consider separately that aspect of the world from which we start, its aspect as knowable, and therefore, in the meantime, we must, without reserve, regard all presented objects, even our own bodies (as we shall presently show more fully), merely as ideas, and call them merely ideas. By so doing we always abstract from will (as we hope to make clear to every one further on), which by itself constitutes the other aspect of the world. For as the world is in one aspect entirely idea, so in another it is entirely will. A reality which is neither of these two, but an object in itself (into which the thing in itself has unfortunately dwindled in the hands of Kant), is the phantom of a dream, and its acceptance is an ignis fatuus in philosophy.
§ 2. That which knows all things and is known by none is the subject. Thus it is the supporter of the world, that condition of all phenomena, of all objects which is always pre-supposed throughout experience; for all that exists, exists only for the subject. Every one finds himself to be subject, yet only in so far as he knows, not in so far as he is an object of knowledge. But his body is object, and therefore from this point of view we call it idea. For the body is an object among objects, and is conditioned by the laws of objects, although it is an immediate object. Like all objects of perception, it lies within the universal forms of knowledge, time and space, which are the conditions of multiplicity. The subject, on the contrary, which is always the knower, never the known, does not come under these forms, but is presupposed by them; it has therefore neither multiplicity nor its opposite unity. We never know it, but it is always the knower wherever there is knowledge.
So then the world as idea, the only aspect in which we consider it at present, has two fundamental, necessary, and inseparable halves. The one half is the object, the forms of which are space and time, and through these multiplicity. The other half is the subject, which is not in space and time, for it is present, entire and undivided, in every percipient being. So that any one percipient being, with the object, constitutes the whole world as idea just as fully as the existing millions could do; but if this one were to disappear, then the whole world as idea would cease to be. These halves are therefore inseparable even for thought, for each of the two has meaning and existence only through and for the other, each appears with the other and vanishes with it. They limit each other immediately; where the object begins the subject ends. The universality of this limitation is shown by the fact that the essential and hence universal forms of all objects, space, time, and causality, may, without knowledge of the object, be discovered and fully known from a consideration of the subject, i.e., in Kantian language, they lie a priori in our consciousness. That he discovered this is one of Kant's principal merits, and it is a great one. I however go beyond this, and maintain that the principle of sufficient reason is the general expression for all these forms of the object of which we are a priori conscious; and that therefore all that we know purely a priori, is merely the content of that principle and what follows from it; in it all our certain a priori knowledge is expressed. In my essay on the principle of sufficient reason I have shown in detail how every possible object comes under it; that is, stands in a necessary relation to other objects, on the one side as determined, on the other side as determining: this is of such wide application, that the whole existence of all objects, so far as they are objects, ideas and nothing more, may be entirely traced to this their necessary relation to each other, rests only in it, is in fact merely relative; but of this more presently. I have further shown, that the necessary relation which the principle of sufficient reason expresses generally, appears in other forms corresponding to the classes into which objects are divided, according to their possibility; and again that by these forms the proper division of the classes is tested. I take it for granted that what I said in this earlier essay is known and present to the reader, for if it had not been already said it would necessarily find its place here.
§ 3. The chief distinction among our ideas is that between ideas of perception and abstract ideas. The latter form just one class of ideas, namely concepts, and these are the possession of man alone of all creatures upon earth. The capacity for these, which distinguishes him from all the lower animals, has always been called reason.5 We shall consider these abstract ideas by themselves later, but, in the first place, we shall speak exclusively of the ideas of perception. These comprehend the whole visible world, or the sum total of experience, with the conditions of its possibility. We have already observed that it is a highly important discovery of Kant's, that these very conditions, these forms of the visible world, i.e., the absolutely universal element in its perception, the common property of all its phenomena, space and time, even when taken by themselves and apart from their content, can, not only be thought in the abstract, but also be directly perceived; and that this perception or intuition is not some kind of phantasm arising