The World as Will and Idea, Vol. II — Arthur Schopenhauer, trans. Haldane & Kemp

p. 65

always see before us only an application of the single and simple law of causality which gives the rule to the sequence of states, but never anything which must be comprehended by means of a new and special function of the understanding.

Or is it perhaps advanced in support of the conception of reciprocity that action and reaction are equal ?

But the reason of this is what I urge so strongly and have fully explained in the essay on the principle of sufficient reason, that the cause and the effect are not two bodies, but two successive states of bodies, consequently each of the two states implicates all bodies concerned ; thus the effect, i.e., ;he newly appearing state, for example, in the case of an impulse, extends to both bodies in the same proportion; therefore the body impelled produces just as great a 3hange in the body impelling as it itself sustains (each in proportion to its mass and velocity).

If one pleases to sail this reciprocity, then absolutely every effect is a reciprocal effect, and no new conception is introduced on bhis account, still less does it require a new function of the understanding, but we only have a superfluous synonym for causality.

But Kant himself, in a moment of thoughtlessness, exactly expressed this view in the " Metaphysical First Principles of Natural Science," at the beginning of the proof of the fourth principle of mechanics : " All external affect in the world is reciprocal effect.

How then should different functions lie a priori in the understanding for simple causality and for reciprocity, and, indeed, how should the real succession of things only be possible and knowable by means of the first, and their co-existence by means of the second ? According to this, if all effect is reciprocal effect, succession and simultaneity would be the same thing, and therefore everything in the world would take place at the same moment.

If there were true reciprocity, then perpetual motion would also be possible, and indeed a priori certain ; but it is rather the case that the a priori conviction that there is no true reciprocity, VOL, 11. B

p. 66

and no corresponding form of the understanding, i the ground of the assertion that perpetual motion impossible.

Aristotle also denies reciprocity in the strict sense ; fo he remarks that two things may certainly be reciprocal causes of each other, but only if this is understood in different sense of each of them; for example, that on acts upon the other as the motive, but the latter ac upon the former as the cause of its movement We find in two passages the same words : Physic, lib. ii. c. 3, and Metaph., lib. v. c. 2. Eari oe riva /ecu aWrfXwp atria' olo\ to iroveiv avriov T779 evef ta<?, tcai avrr) rov ttovuv' a\X' o top avrov rpoirov, aXKa to pep <o<? re\o9, to 6c a>9 apxt Kivrjo-em. (Sunt prosterea qua sibi sunt mutiio cuusce, ut exercitium bonce habitudinis, et hcec exereitii : ai non corfem modo, sed hcec ut finis, aliud ut principium motus.) Ify besides this, he had accepted a reciprocity proper, he would have introduced it here, for in both passages he is concerned with enumerating all the possible kinds of causes. In the Analyt. post., lib. ii c. 11, he speaks of a circle of causes and effects, but not of reciprocity.

4. The categories of Modality have this advantage over all others, that what is expressed through each of them really corresponds to the form of judgment from which it is derived; which with the other categories is scarcely ever the case, because for the most part they are deduced | from the forms of judgment with the most capriciomj violence.