| All determination in regard to time presupposes the existence of something permanent in perception. |
| But this permanent something cannot be something in me, for the very reason that my existence in time is itself determined by this permanent something. |
| It follows that the perception of this permanent existence is possible only through a thing without me and not through the mere representation of a thing without me. |
| Consequently, the determination of my existence in time is possible only through the existence of real things external to me. |
| Now, consciousness in time is necessarily connected with the consciousness of the possibility of this determination in time. |
| Hence it follows that consciousness in time is necessarily connected also with the existence of things without me, inasmuch as the existence of these things is the condition of determination in time. |
| That is to say, the consciousness of my own existence is at the same time an immediate consciousness of the existence of other things without me. |
| Remark I. The reader will observe, that in the foregoing proof the game which idealism plays is retorted upon itself, and with more justice. |
| It assumed that the only immediate experience is internal and that from this we can only infer the existence of external things. |
| But, as always happens, when we reason from given effects to determined causes, idealism has reasoned with too much haste and uncertainty, for it is quite possible that the cause of our representations may lie in ourselves, and that we ascribe it falsely to external things. |
| But our proof shows that external experience is properly immediate,* that only by virtue of it--not, indeed, the consciousness of our own existence, but certainly the determination of our existence in time, that is, internal experience--is possible. |
| It is true, that the representation "I am," which is the expression of the consciousness which can accompany all my thoughts, is that which immediately includes the existence of a subject. |
| But in this representation we cannot find any knowledge of the subject, and therefore also no empirical knowledge, that is, experience. |
| For experience contains, in addition to the thought of something existing, intuition, and in this case it must be internal intuition, that is, time, in relation to which the subject must be determined. |
| But the existence of external things is absolutely requisite for this purpose, so that it follows that internal experience is itself possible only mediately and through external experience. |
| [*Footnote; The immediate consciousness of the existence of external things is, in the preceding theorem, not presupposed, but proved, by the possibility of this consciousness understood by us or not. |
| The question as to the possibility of it would stand thus; "Have we an internal sense, but no external sense, and is our belief in external perception a mere delusion?" But it is evident that, in order merely to fancy to ourselves anything as external, that is, to present it to the sense in intuition we must already possess an external sense, and must thereby distinguish immediately the mere receptivity of an external intuition from the spontaneity which characterizes every act of imagination. |
| For merely to imagine also an external sense, would annihilate the faculty of intuition itself which is to be determined by the imagination.] |
| Remark II. Now with this view all empirical use of our faculty of cognition in the determination of time is in perfect accordance. |
| Its truth is supported by the fact that it is possible to perceive a determination of time only by means of a change in external relations (motion) to the permanent in space (for example, we become aware of the sun's motion by observing the changes of his relation to the objects of this earth). |
| But this is not all. |