| For this reason, every transition in perception to anything which follows upon another in time, is a determination of time by means of the production of this perception. |
| And as this determination of time is, always and in all its parts, a quantity, the perception produced is to be considered as a quantity which proceeds through all its degrees--no one of which is the smallest possible--from zero up to its determined degree. |
| From this we perceive the possibility of cognizing a priori a law of changes--a law, however, which concerns their form merely. |
| We merely anticipate our own apprehension, the formal condition of which, inasmuch as it is itself to be found in the mind antecedently to all given phenomena, must certainly be capable of being cognized a priorI. Thus, as time contains the sensuous condition a priori of the possibility of a continuous progression of that which exists to that which follows it, the understanding, by virtue of the unity of apperception, contains the condition a priori of the possibility of a continuous determination of the position in time of all phenomena, and this by means of the series of causes and effects, the former of which necessitate the sequence of the latter, and thereby render universally and for all time, and by consequence, objectively, valid the empirical cognition of the relations of time. |
| C. THIRD ANALOGY. |
| Principle of Coexistence, According to the Law of Reciprocity or Community. |
| All substances, in so far as they can be perceived in space at the same time, exist in a state of complete reciprocity of action. |
| PROOF. |
| Things are coexistent, when in empirical intuition the perception of the one can follow upon the perception of the other, and vice versa-- which cannot occur in the succession of phenomena, as we have shown in the explanation of the second principle. |
| Thus I can perceive the moon and then the earth, or conversely, first the earth and then the moon; and for the reason that my perceptions of these objects can reciprocally follow each other, I say, they exist contemporaneously. |
| Now coexistence is the existence of the manifold in the same time. |
| But time itself is not an object of perception; and therefore we cannot conclude from the fact that things are placed in the same time, the other fact, that the perception of these things can follow each other reciprocally. |
| The synthesis of the imagination in apprehension would only present to us each of these perceptions as present in the subject when the other is not present, and contrariwise; but would not show that the objects are coexistent, that is to say, that, if the one exists, the other also exists in the same time, and that this is necessarily so, in order that the perceptions may be capable of following each other reciprocally. |
| It follows that a conception of the understanding or category of the reciprocal sequence of the determinations of phenomena (existing, as they do, apart from each other, and yet contemporaneously), is requisite to justify us in saying that the reciprocal succession of perceptions has its foundation in the object, and to enable us to represent coexistence as objective. |
| But that relation of substances in which the one contains determinations the ground of which is in the other substance, is the relation of influence. |
| And, when this influence is reciprocal, it is the relation of community or reciprocity. |
| Consequently the coexistence of substances in space cannot be cognized in experience otherwise than under the precondition of their reciprocal action. |
| This is therefore the condition of the possibility of things themselves as objects of experience. |
| Things are coexistent, in so far as they exist in one and the same time. |
| But how can we know that they exist in one and the same time? |
| Only by observing that the order in the synthesis of apprehension of the manifold is arbitrary and a matter of indifference, that is to say, that it can proceed from A, through B, C, D, to E, or contrariwise from E to A. |