As primary fact, the cause is qualified as having absolute independence and a subsistence maintained in face of the effect: but in the necessity, whose identity constitutes that primariness itself, it is wholly passed into the effect. So far again as we can speak of a definite content, there is no content in the effect that is not in the cause. That identity in fact is the absolute content itself: but it is no less also the form-characteristic. The primariness of the cause is suspended in the effect in which the cause makes itself a dependent being. The cause however does not for that reason vanish and leave the effect to be alone actual. For this dependency is in like manner directly suspended, and is rather the reflection of the cause in itself, its primariness: in short, it is in the effect that the cause first becomes actual and a cause. The cause consequently is in its full truth causa sui.—Jacobi, sticking to the partial conception of mediation (in his Letters on Spinoza, second edit. p. 416), has treated the causa sui (and the effectus sui is the same), which is the absolute truth of the cause, as a mere formalism. He has also made the remark that God ought to be defined not as the ground of things, but essentially as cause. A more thorough consideration of the nature of cause would have shown that Jacobi did not by this means gain what he intended. Even in the finite cause and its conception we can see this identity between cause and effect in point of content. The rain (the cause) and the wet (the effect) are the self-same existing water. In point of form the cause (rain) is dissipated or lost in the effect (wet): but in that case the result can no longer be described as effect; for without the cause it is nothing, and we should have only the unrelated wet left.

In the common acceptation of the causal relation the cause is finite, to such extent as its content is so (as is also the case with finite substance), and so far as cause and effect are conceived as two several independent existences; which they are, however, only when we leave the causal relation out of sight. In the finite sphere we never get over the difference of the form-characteristics in their relation: and hence we turn the matter round and define the cause also as something dependent or as an effect. This again has another cause, and thus there grows up a progress from effects to causes ad infinitum. There is a descending progress too: the effect, looked at in its identity with the cause, is itself defined as a cause, and at the same time as another cause, which again has other effects, and so on for ever.

The way understanding bristles up against the idea of substance is equalled by its readiness to use the relation of cause and effect. Whenever it is proposed to view any sum of fact as necessary, it is especially the relation of causality to which the reflective understanding makes a point of tracing it back. Now, although this relation does undoubtedly belong to necessity, it forms only one aspect in the process of that category. That process equally requires the suspension of the mediation involved in causality and the exhibition of it as simple self-relation. If we stick to causality as such, we have it not in its truth. Such a causality is merely finite, and its finitude lies in retaining the distinction between cause and effect unassimilated. But these two terms, if they are distinct, are also identical. Even in ordinary consciousness that identity may be found. We say that a cause is a cause, only when it has an effect, and vice versâ. Both cause and effect are thus one and the same content: and the distinction between them is primarily only that the one lays down, and the other is laid down. This formal difference however again suspends itself, because the cause is not only a cause of something else, but also a cause of itself; while the effect is not only an effect of something else, but also an effect of itself. The finitude of things consists accordingly in this. While cause and effect are in their notion identical, the two forms present themselves severed so that, though the cause is also an effect, and the effect also a cause, the cause is not an effect in the same connexion as it is a cause, nor the effect a cause in the same connexion as it is an effect. This again gives the infinite progress, in the shape of an endless series of causes, which shows itself at the same time as an endless series of effects.

154.] The effect is different from the cause. The former as such has a being dependent on the latter. But such a dependence is likewise reflection-into-self and immediacy: and the action of the cause, as it constitutes the effect, is at the same time the pre-constitution of the effect, so long as effect is kept separate from cause. There is thus already in existence another substance on which the effect takes place. As immediate, this substance is not a self-related negativity and active, but passive. Yet it is a substance, and it is therefore active also: it therefore suspends the immediacy it was originally put forward with, and the effect which was put into it: it reacts, i.e. suspends the activity of the first substance. But this first substance also in the same way sets aside its own immediacy, or the effect which is put into it; it thus suspends the activity of the other substance and reacts. In this manner causality passes into the relation of Action and Reaction, or Reciprocity.

In Reciprocity, although causality is not yet invested with its true characteristic, the rectilinear movement out from causes to effects, and from effects to causes, is bent round and back into itself, and thus the progress ad infinitum of causes and effects is, as a progress, really and truly suspended. This bend, which transforms, the infinite progression into a self-contained relationship, is here as always the plain reflection that in the above meaningless repetition there is only one and the same thing, viz. one cause and another, and their connexion with one another. Reciprocity—which is the development of this relation-itself however only distinguishes turn and turn about (—not causes, but) factors of causation, in each of which—just because they are inseparable (on the principle of the identity that the cause is cause in the effect, and vice versâ)—the other factor is also equally supposed.

(c) Reciprocity or Action and Reaction.

155.] The characteristics which in Reciprocal Action are retained as distinct are (α) potentially the same. The one side is a cause, is primary, active, passive, &c., just as the other is. Similarly the pre-supposition of another side and the action upon it, the immediate primariness and the dependence produced by the alternation, are one and the same on both sides. The cause assumed to be first is on account of its immediacy passive, a dependent being, and an effect. The distinction of the causes spoken of as two is accordingly void: and properly speaking there is only one cause, which, while it suspends itself (as substance) in its effect, also rises in this operation only to independent existence as a cause.

156.] But this unity of the double cause is also (β) actual. All this alternation is properly the cause in act of constituting itself and in such constitution lies its being. The nullity of the distinctions is not only potential, or a reflection of ours (§ 155). Reciprocal action just means that each characteristic we impose is also to be suspended and inverted into its opposite, and that in this way the essential nullity of the 'moments' is explicitly stated. An effect is introduced into the primariness; in other words, the primariness is abolished: the action of a cause becomes reaction, and so on.

Reciprocal action realises the causal relation in its complete development. It is this relation, therefore, in which reflection usually takes shelter when the conviction grows that things can no longer be studied satisfactorily from a causal point of view, on account of the infinite progress already spoken of. Thus in historical research the question may be raised in a first form, whether the character and manners of a nation are the cause of its constitution and its laws, or if they are not rather the effect. Then, as the second step, the character and manners on one side and the constitution and laws on the other are conceived on the principle of reciprocity: and in that case the cause in the same connexion as it is a cause will at the same time be an effect, and vice versâ. The same thing is done in the study of Nature, and especially of living organisms. There the several organs and functions are similarly seen to stand to each other in the relation of reciprocity. Reciprocity is undoubtedly the proximate truth of the relation of cause and effect, and stands, so to say, on the threshold of the notion; but on that very ground, supposing that our aim is a thoroughly comprehensive idea, we should not rest content with applying this relation. If we get no further than studying a given content under the point of view of reciprocity, we are taking up an attitude which leaves matters utterly incomprehensible. We are left with a mere dry fact; and the call for mediation, which is the chief motive in applying the relation of causality, is still unanswered. And it we look more narrowly into the dissatisfaction felt in applying the relation of reciprocity, we shall see that it consists in the circumstance, that this relation, instead of being treated as an equivalent for the notion, ought, first of all, to be known and understood in its own nature. And to understand the relation of action and reaction we must not let the two sides rest in their state of mere given facts, but recognise them, as has been shown in the two paragraphs preceding, for factors of a third and higher, which is the notion and nothing else. To make, for example, the manners of the Spartans the cause of their constitution and their constitution conversely the cause of their manners, may no doubt be in a way correct. But, as we have comprehended neither the manners nor the constitution of the nation, the result of such reflections can never be final or satisfactory. The satisfactory point will be reached only when these two, as well as all other, special aspects of Spartan life and Spartan history are seen to be founded in this notion.

157.] This pure self-reciprocation is therefore Necessity unveiled or realised. The link of necessity quâ necessity is identity, as still inward and concealed, because it is the identity of what are esteemed actual things, although their very self-subsistence is bound to be necessity. The circulation of substance through causality and reciprocity therefore only expressly makes out or states that self-subsistence is the infinite negative self-relation—a relation negative, in general, for in it the act of distinguishing and intermediating becomes a primariness of actual things independent one against the other,—and infinite self-relation, because their independence only lies in their identity.