The World as Will and Idea (Vol. 2 of 3). Артур Шопенгауэр
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a succession of causes and effects of the same names, and throughout nothing essentially different from simple causality. This is also the case with the swinging of the pendulum, and indeed also with the self-conservation of the organised body, in which case likewise every state introduces a new one, which is of the same kind as that by which it was itself brought about, but individually is new. Only here the matter is complicated, because the chain no longer consists of links of two kinds, but of many kinds, so that a link of the same name only recurs after several others have intervened. But we 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., the 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 change in the body impelling as it itself sustains (each in proportion to its mass and velocity). If one pleases to call this reciprocity, then absolutely every effect is a reciprocal effect, and no new conception is introduced on this 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 effect 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, and no corresponding form of the understanding, is the ground of the assertion that perpetual motion is impossible.
Aristotle also denies reciprocity in the strict sense; for he remarks that two things may certainly be reciprocal causes of each other, but only if this is understood in a different sense of each of them; for example, that one acts upon the other as the motive, but the latter acts 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. Εστι δε τινα και αλληλων αιτια; οἱον το πονειν αιτιον της ευεξιας, και αὑτη του πονειν; αλλ᾽ ου τον αυτον τροπον, αλλα το μεν ὡς τελος, το δε ὡς αρχη κινησεως. (Sunt præterea quæ sibi sunt mutuo causæ, ut exercitium bonæ habitudinis, et hæc exercitii: at non eodem modo, sed hæc ut finis, aliud ut principium motus.) If, 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 capricious violence.
Thus that it is the conceptions of the possible, the actual, and the necessary which occasion the problematic, assertatory, and apodictic forms of judgment, is perfectly true; but that those conceptions are special, original forms of knowledge of the understanding which cannot be further deduced is not true. On the contrary, they spring from the single original form of all knowledge, which is, therefore, known to us a priori, the principle of sufficient reason; and indeed out of this the knowledge of necessity springs directly. On the other hand, it is only because reflection is applied to this that the conceptions of contingency, possibility, impossibility, and actuality arise. Therefore all these do not by any means spring from one faculty of the mind, the understanding, but arise through the conflict of abstract and intuitive knowledge, as will be seen directly.
I hold that to be necessary and to be the consequent of a given reason are absolutely interchangeable notions, and completely identical. We can never know, nor even think, anything as necessary, except so far as we regard it as the consequent of a given reason; and the conception of necessity contains absolutely nothing more than this dependence, this being established through something else, and this inevitable following from it. Thus it arises and exists simply and solely through the application of the principle of sufficient reason. Therefore, there is, according to the different forms of this principle, a physical necessity (the effect from the cause), a logical (through the ground of knowing, in analytical judgments, syllogisms, &c.), a mathematical (according to the ground of being in time and space), and finally a practical necessity, by which we intend to signify not determination through a pretended categorical imperative, but the necessary occurrence of an action according to the motives presented, in the case of a given empirical character. But everything necessary is only so relatively, that is, under the presupposition of the reason from which it follows; therefore absolute necessity is a contradiction. With regard to the rest, I refer to § 49 of the essay on the principle of sufficient reason.
The contradictory opposite, i. e., the denial of necessity, is contingency. The content of this conception is, therefore, negative – nothing more than this: absence of the connection expressed by the principle of sufficient reason. Consequently the contingent is also always merely relative. It is contingent in relation to something which is not its reason. Every object, of whatever kind it may be – for example, every event in the actual world – is always at once necessary and contingent, necessary in relation to the one condition which is its cause: contingent in relation to everything else. For its contact in time and space with everything else is a mere coincidence without necessary connection: hence also the words chance, συμπτωμα, contingens. Therefore an absolute contingency is just as inconceivable as an absolute necessity. For the former would be simply an object which stood to no other in the relation of consequent to its reason. But the inconceivability of such a thing is just the content of the principle of sufficient reason negatively expressed, and therefore this principle must first be upset before we can think an absolute contingency; and even then it itself would have lost all significance, for the conception of contingency has meaning only in relation to that principle, and signifies that two objects do not stand to each other in the relation of reason and consequent.
In nature, which consists of ideas of perception, everything that happens is necessary; for it proceeds from its cause. If, however, we consider this individual with reference to everything else which is not its cause, we know it as contingent; but this is already an abstract reflection. Now, further, let us abstract entirely from a natural object its causal relation to everything else, thus its necessity and its contingency; then this kind of knowledge comprehends the conception of the actual, in which one only considers the effect, without looking for the cause, in relation to which one would otherwise have to call it necessary, and in relation to everything else contingent. All this rests ultimately upon the fact that the modality of the judgment does not indicate so much the objective nature of things as the relation of our knowledge to them. Since, however, in nature everything proceeds from a cause, everything actual is also necessary, yet only so far as it is at this time, in this place; for only so far does determination by the law of causality extend. Let us leave, however, concrete nature and pass over to abstract thinking; then we can present to ourselves in reflection all the natural laws which are known to us partly a priori, partly only a posteriori, and this abstract idea contains all that is in nature at any time, in any place, but with abstraction