infinity in both directions; these are matter and the forces of nature. They are both conditions of causality, while everything else is conditioned by it. For the one (matter) is that in which the states and their changes appear; the other (forces of nature) is that by virtue of which alone they can appear at all. Here, however, one must remember that in the second book, and later and more thoroughly in "The Will in Nature," the natural forces are shown to be identical with the will in us; but matter appears as the mere visibility of the will; so that ultimately it also may in a certain sense be regarded as identical with the will.
On the other hand, not less true and correct is what is explained in § 4 of the first book, and still better in the second edition of the essay on the principle of sufficient reason at the end of § 21, p. 77 (third edition, p. 82), that matter is causality itself objectively comprehended, for its entire nature consists in acting in general, so that it itself is thus the activity (ενεργεια = reality) of things generally, as it were the abstraction of all their different kinds of acting. Accordingly, since the essence, essentia, of matter consists in action in general, and the reality, existentia, of things consists in their materiality, which thus again is one with action in general, it may be asserted of matter that in it existentia and essentia unite and are one, for it has no other attribute than existence itself in general and independent of all fuller definitions of it. On the other hand, all empirically given matter, thus all material or matter in the special sense (which our ignorant materialists at the present day confound with matter), has already entered the framework of the forms and manifests itself only through their qualities and accidents, because in experience every action is of quite a definite and special kind, and is never merely general. Therefore pure matter is an object of thought alone, not of perception, which led Plotinus (Enneas II., lib. iv., c. 8 & 9) and Giordano Bruno (Della Causa, dial. 4) to make the paradoxical assertion that
