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
