(c.) Disjunctive judgments spring from the law of thought of excluded third, which is a metalogical truth; they are, therefore, entirely the property of the reason, and have not their origin in the understanding. The deduction of the category of community or reciprocity from them is, however, a glaring example of the violence which Kant sometimes allowed to be done to truth, merely in order to satisfy his love of architectonic symmetry. The illegitimacy of that deduction has already often been justly condemned and proved upon various grounds, especially by G. E. Schulze in his “Kritik der theoretischen Philosophie,” and by Berg in his “Epikritik der Philosophie.” What real analogy is there, indeed, between the problematical determination of a concept by disjunctive predicates and the thought of reciprocity? The two are indeed absolutely opposed, for in the disjunctive judgment the actual affirmation of one of the two alternative propositions is also necessarily the negation of the other; if, on the other hand, we think two things in the relation of reciprocity, the affirmation of one is also necessarily the affirmation of the other, and vice versa. Therefore, unquestionably, the real logical analogue of reciprocity is the vicious circle, for in it, as nominally in the case of reciprocity, what is proved is also the proof, and conversely. And just as logic rejects the vicious circle, so the conception of reciprocity ought to be banished from metaphysics. For I now intend, quite seriously, to prove that there is no reciprocity in the strict sense, and this conception, which people are so fond of using, just on account of the indefiniteness of the thought, is seen, if more closely considered, to be empty, false, and invalid. First of all, the reader must call to mind what causality really is, and to assist my exposition, see upon this subject § 20 of the introductory essay, also my prize-essay on the freedom of the will, chap. iii. p. 27 seq., and lastly the fourth chapter of the second book of this work. Causality is the law according to which the conditions or states of matter which appear determine their position in time. Causality has to do merely with conditions or states, indeed, properly, only with changes, and neither with matter as such, nor with permanence without change. Matter, as such, does not come under the law of causality, for it neither comes into being nor passes away; thus neither does the whole thing, as we commonly express ourselves, come under this law, but only the conditions or states of matter. Further, the law of causality has nothing to do with permanence, for where nothing changes there is no producing of effects and no causality, but a continuing quiet condition or state. But if, now, such a state is changed, then the new state is either again permanent or it is not, but immediately introduces a third state, and the necessity with which this happens is just the law of causality, which is a form of the principle of sufficient reason, and therefore cannot be further explained, because the principle of sufficient reason is the principle of all explanation and of all necessity. From this it is clear that cause and effect stand in intimate connection with, and necessary relation to, the course of time. Only because the state A. precedes in time the state B., and their succession is necessary and not accidental, i. e., no mere sequence but a consequence – only because of this is the state A. cause and the state B. effect. The conception reciprocity, however, contains this, that both are cause and both are effect of each other; but this really amounts to saying that each of the two is the earlier and also the later; thus it is an absurdity. For that both states are simultaneous, and indeed necessarily simultaneous, cannot be admitted, because, as necessarily belonging to each other and existing at the same time, they constitute only one state. For the permanence of this state there is certainly required the continued existence of all its determinations, but we are then no longer concerned with change and causality, but with duration and rest, and nothing further is said than that if one determination of the whole state be changed, the new state which then appears cannot continue, but becomes the cause of the change of all the other determinations of the first state, so that a new third state appears; which all happens merely in accordance with the simple law of causality, and does not establish a new law, that of reciprocity.
I also definitely assert that the conception reciprocity cannot be supported by a single example. Everything that one seeks to pass off as such is either a state of rest, to which the conception of causality, which has only significance with reference to changes, finds no application at all, or else it is an alternating succession of states of the same name which condition each other, for the explanation of which simple causality is quite sufficient. An example of the first class is afforded by a pair of scales brought to rest by equal weights. Here there is no effect produced, for there is no change; it is a state of rest; gravity acts, equally divided, as in every body which is supported at its centre of gravity, but it cannot show its force by any effect. That the taking away of one weight produces a second state, which at once becomes the cause of the third, the sinking of the other scale, happens according to the simple law of cause and effect, and requires no special category of the understanding, and not even a special name. An example of the second class is the continuous burning of a fire. The combination of oxygen with the combustible body is the cause of heat, and heat, again, is the cause of the renewed occurrence of the chemical combination. But this is nothing more than a chain of causes and effects, the links of which have alternately the same name. The burning, A., produces free heat, B., this produces new burning, C. (i. e., a new effect which has the same name as the cause A., but is not individually identical with it), this produces new heat, D. (which is not really identical with the effect B., but only according to the concept, i. e., it has the same name), and so on indefinitely. A good example of what in ordinary life is called reciprocity is afforded by a theory about deserts given by Humboldt (Ansichten der Natur, 2d ed., vol. ii. p. 79). In the sandy deserts it does not rain, but it rains upon the wooded mountains surrounding them. The cause is not the attraction of the clouds by the mountains; but it is the column of heated air rising from the sandy plain which prevents the particles of vapour from condensing, and drives the clouds high into the heavens. On the mountains the perpendicular rising stream of air is weaker, the clouds descend, and the rainfall ensues in the cooler air. Thus, want of rain and the absence of plants in the desert stand in the relation of reciprocity; it does not rain because the heated sand-plain