495. The dyadic requirement of the law of time is that if a subject existentially receives contrary attributes, of the two contrary states an existentially determinate one is first in the existential order of evolution and second in the existential order of involution, while the other is second in the existential order of evolution and first in the existential order of involution; and of any two events whatever, a determinate one is related to the other in this same way (although the two events are not joined, as the two states are joined in the event), unless they are independent of one another, or contemporaneous. Suppose I hold in my hand a leaden ball. I open my hand, the ball falls to the ground and rests there. There are three states of the ball: first, the ball is in my hand and is not on the ground; second, the ball is not in my hand and is not on the ground; third, the ball is not in my hand and is on the ground. Of the two events, the ball's leaving my hand and the ball's striking the ground, the former consists in the junction of the ball's being in my hand as first in evolution and the ball's being out of my hand as second in evolution. Hence, of the two states, the ball is in my hand but not on the ground and the ball is neither in my hand nor on the ground, the former is necessarily the first in evolution, being made so by the event. And of the two states, the ball is neither in my hand nor on the ground and the ball is not in my hand but is on the ground, the event of striking makes the former to be first in evolution. Thus, the order of the states is controlled by the nature of the events. But the events are nothing in themselves. But if the fall were instantaneous, if for example my hand intercepted at first a visual ray and were then removed, so that there were but two states — first, the hand visible, the ground invisible; second, the hand invisible, the ground visible — then the two events are contemporaneous. If the two states, first »P and Q,« second »not P and not Q« exist, then only one of the two states »P but not Q« and »Q but not P« can exist, for the reason that it is the dyadic character of the events that decides. Thus, supposing state »P and Q« and state »neither P nor Q« to both exist, and supposing that in the event »P - not P,« P is first in evolution, then the state "P and Q« must antecede the state »neither P nor Q« in evolution, and consequently in the event »Q - not Q,« Q must antecede not Q in evolution. These two events, »P becomes not P« and »Q becomes not Q,« may then either antecede the other in evolution, and according as one or other antecedes, one or other of the two states, »P but not Q,« and »not P but Q,« becomes impossible. If the two events are contemporaneous, neither being existentially determined to be first in evolution, then these two states are both impossible.

496. The three possible temporal relations between two instantaneous events are naturally felt by us to mirror the three possible logical relations of two propositions which can be both true or both false, but are not logically equivalent (that is, have not by logical necessity the same value, as to being true or false). Namely of two such propositions, A and B, either, first, A can be false though B is true, but B must be true should A be true, or, second, either can be false though the other be true, so that they are independent of one another, or, third, A must be true should B be true, but B can be false though A is true. It is remarkable that we should instinctively connect the first case with the temporal succession of B after A, and the third case with the temporal succession of A after B, saying, in the former case, that B would follow from A and, in the latter, that A would follow from B. For superficial resemblances are the other way. We know what precedes in time from that which succeeds it much better than we know what is to come from that which goes before. This shows the instinct is not due to superficial resemblances. It is true that we know the conclusion later than we know the premisses; but we do not so much think of our knowledge as following as we do that one fact is logically sequent on the other. The instinct may, therefore, be presumed to be an obscure perception that temporal succession is a mirror of, or framework for, logical sequence. Thus instinct with its almost unerring certainty favors this doctrine.

497. That of two events not contemporaneous one should happen before the other involves a thisness and thus a dyadism. For as it is impossible for us to indicate or ascertain one to be first by any general quality but only by a comparison with some standard experience, so it is impossible for a distinction of first and second to be except by a dyadic force of existence. That a determinate one shall be first and the other second requires reference to some kind of standard, since right and left are, as far as any monadic quality goes, just alike. There must be a standard first and second, and for any other pair there must be some way of bringing them into experiential connection one way and not the other way with this standard. This experiential reference to a standard in knowledge corresponds to an existential dyadic connection in fact. Otherwise there would be no truth in the knowledge.