in causality demands more than this, and hence in order to realize itself the conception becomes that of reciprocity. A preliminary effort to remove the difficulty may be made by conceiving an endless chain of causes each of which is the effect of a preceding cause and the cause of a subsequent effect.[1] This, however, gives inadequate satisfaction to the identity of causality stated in the doctrine of causa sui; and we are forced to the conception of reciprocity. The nature of the effect depends not only on the cause, but also on the passive factor, i.e. that in which the effect is produced. The cause does not act in the void, but presupposes something else on which to operate. The so-called passive factor must therefore be conceived as cause with reference to this event, and not merely to a subsequent one; for without it the cause would not have its character as active. Further, the form of activity exercised by the cause depends on and varies with the other factor; hence the result is the common product of an interaction. Causality thus implies an action and reaction of elements in which each is both cause and effect of the other; each becomes itself in determining the other.
It is through the conception of reciprocity that we pass beyond the sphere of essence altogether; and we must be careful to note exactly where we stand. In tracing substance into the truer category of reciprocity it is important that the positive side of the former should not be lost. We have seen substance sunder itself into individual factors which were respectively cause and effect, and we insisted that it is still one substance which appears thus. Cause and effect are two and also one; and we have refused to lighten the difficulty by casting overboard the aspect of unity. For the position does not become any easier in that way, and the case becomes without remedy if we assume that we are dealing with inherently indifferent and unrelated factors. This remains true of reciprocity, and we are faced with the same problem still. When the world is thought under the conception of reciprocity it becomes a system of mutually determining parts,
- ↑ ‘Thus the cause has an effect, and is itself effect; and the effect not only has a cause but is itself cause. But the effect which the cause has, and the effect which it is—like the cause which the effect has, and the cause which it is—are distinct’ (Larger Logic, WW. IV. pp. 234-5).
