may be in itself. In the first respect, our conclusion was that it is objective activity in general, yet conceived without fuller determination; therefore it takes the place of causality in the table of our a priori knowledge which is given there. For what is material is that which acts (the actual) in general, and regarded apart from the specific nature of its action. Hence also matter, merely as such, is not an object of perception, but only of thought, and thus is really an abstraction. It only comes into perception in connection with form and quality, as a body, i. e., as a fully determined kind of activity. It is only by abstracting from this fuller determination that we think of matter as such, i. e., separated from form and quality; consequently under matter we think of acting absolutely and in general, thus of activity in the abstract. The more fully determined acting we then conceive as the accident of matter; but only by means of this does matter become perceptible, i. e., present itself as a body and an object of experience. Pure matter, on the other hand, which, as I have shown in the Criticism of the Kantian Philosophy, alone constitutes the true and admissible content of the conception of substance, is causality itself, thought objectively, consequently as in space, and therefore filling it. Accordingly the whole being of matter consists in acting. Only thus does it occupy space and last in time. It is through and through pure causality. Therefore wherever there is action there is matter, and the material is the active in general. But causality itself is the form of our understanding; for it is known to us a priori, as well as time and space. Thus matter also, so far and up to this point, belongs to the formal part of our knowledge, and is consequently that form of the understanding, causality itself, bound up with space and time, hence objectified, i. e., conceived as that which fills space. (The fuller explanation of this doctrine will be found in the second edition of the essay on the principle of sufficient reason, p. 77; third edition, p. 82.) So far, however, matter is properly not the object but the condition of experience; like the pure understanding itself, whose function it so far is. Therefore of pure matter there is also only a conception, no perception. It enters into all external experience as a necessary constituent part of it; yet it cannot be given in any experience, but is only thought, and thought indeed as that which is absolutely inert, inactive, formless, and without qualities, and which is yet the supporter of all forms, qualities, and effects. Accordingly, of all fleeting phenomena, thus of all manifestations of natural forces and all living beings, matter is the permanent substratum which is necessarily produced by the forms of our intellect in which the world as idea exhibits itself. As such, and as having sprung from the forms of the intellect, it is entirely indifferent to those phenomena themselves, i. e., it is just as ready to be the supporter of this force of nature as of that, whenever, under the guidance of causality, the necessary conditions appear; while it itself, just because its existence is really only formal, i. e., is founded in the intellect must be thought as that which under all that change is absolutely permanent, thus with regard to time is without beginning and without end. This is why we cannot give up the thought that anything may be made out of anything, for example, gold out of lead; for this would only require that we should find out and bring about the intermediate states which matter, in itself indifferent, would have to pass through upon that path. For a priori we can never see why the same matter which is now the supporter of the quality lead could not some time become the supporter of the quality gold. Matter, as that which is only thought a priori, is distinguished from the a priori intuitions or perceptions proper by the fact that we can also think it entirely away; space and time, on the contrary, never. But this only shows that we can present to ourselves space and time in imagination without matter. For the matter which has once been placed in them, and accordingly thought as existing, we can never again absolutely think away, i. e., imagine it as vanished and annihilated, but are always forced to think of it merely as transferred to another space. So far, then, matter is as inseparably connected with our faculty of knowledge as space and time themselves. Yet even the difference that it must first be voluntarily thought as existing indicates that it does not belong so entirely and in every regard to the formal part of our knowledge as space and time, but also contains an element which is only given a posteriori. It is, in fact, the point of connection of the empirical part of our knowledge with the pure and a priori part, consequently the peculiar foundation-stone of the world of experience.
Only where all a priori assertions cease, therefore in the entirely empirical part of our knowledge of bodies, in their form, quality, and definite manner of acting, does that will reveal itself which we have already recognised and established as the true inner nature of things. But these forms and qualities always appear only as the properties and manifestations of that very matter the existence and nature of which depends upon the subjective forms of our intellect, i. e., they only become visible in it, and therefore by means of it. For that which always exhibits itself to us is only matter acting in some specially determined manner. Out of the inner properties of such matter, properties which cannot be further explained, proceeds every definite kind of effect of given bodies; and yet the matter itself is never perceived, but only these effects, and the definite properties which lie at their foundation, after separating which, matter, as that which then remains over, is necessarily added in thought by us; for, according to the exposition given above, it is objectified causality itself. Accordingly matter is that whereby the will, which constitutes the inner nature of things, becomes capable of being apprehended, perceptible, visible. In this sense, then, matter is simply the visibility of the will, or the bond between the world as will and the world as idea. It belongs to the latter inasmuch as it is the product of the functions of the intellect, to the former inasmuch as that which manifests itself in all material existences, i. e., phenomena is the will. Therefore every object is, as thing in itself, will, and as phenomenon, matter. If we could strip any given matter of all the properties that come to it a priori, i. e., of all the forms of our perception and apprehension, we would have left the thing in itself, that which, by means of those forms, appears as the purely empirical in matter, but which would then itself no longer appear as something extended and active; i. e., we would no longer have matter before us, but the will. This very thing in itself, or the will, in that it becomes a phenomenon, i. e., enters the forms of our intellect, appears as matter, i. e., as the invisible but necessarily assumed supporter of the properties which are only visible through it. In this sense, then, matter is the visibility of the will. Consequently Plotinus and Giordano Bruno were right, not only in their sense but also in ours, when they made the paradoxical assertion already referred to in chapter 4: Matter itself is not extended, consequently it is incorporeal. For space, which is our form of perception, imparts extension to matter, and corporeal existence consists in acting, which depends upon causality, and consequently upon the form of our understanding. On the other hand, every definite property, thus everything empirical in matter, even gravity, depends upon that which only becomes visible by means of matter, the thing in itself, the will. Gravity is yet the lowest of all grades of the objectification of the will; therefore it appears in all matter without exception, thus is inseparable from matter in general. Yet, just because it is a manifestation of the will, it belongs to knowledge a posteriori, not to knowledge a priori. Therefore we can always picture to ourselves matter without weight, but not without extension, repulsive force, and stability, for then it would be without impenetrability, and consequently would not occupy space, i. e., it would be without the power of acting; but the nature of matter as such just consists in acting, i. e., in causality in general; and causality depends upon the a priori form of our understanding, and therefore cannot be thought away.
Matter is accordingly the will itself, but no longer in itself, but so far as it is perceived, i. e., assumes the form of the objective idea. Thus what objectively is matter is subjectively will. Exactly corresponding to this, as was proved above, our body is just the visibility, objectivity of our will, and so also every body is the objectivity of the will at some one of its grades. Whenever the will exhibits itself to objective knowledge it enters into the forms of perception of the intellect, time, space, and causality. But on account of this it exists at once as a material object. We can present to our minds form without matter, but not
