of this kind. For if the smallest empirical element of thought, if any particular perception of my internal state, were to be introduced among the grounds of cognition of this science, it would not be a rational, but an empirical doctrine of the soul. We have thus before us a pretended science, raised upon the single proposition, "I think," whose foundation or want of foundation we may very properly, and agreeably with the nature of a transcendental philosophy, here examine. It ought not to be objected that in this proposition, which expresses the perception of one's self, an internal experience is asserted, and that consequently the rational doctrine of the soul which is founded upon it, is not pure, but partly founded upon an empirical principle. For this internal perception is nothing more than the mere apperception, "I think," which in fact renders all transcendental conceptions possible, in which we say, "I think substance, cause, etc." For internal experience in general and its possibility, or perception in general, and its relation to other perceptions, unless some particular distinction or determination thereof is empirically given, cannot be regarded as empirical cognition, but as cognition of the empirical, and belongs to the investigation of the possibility of every experience, which is certainly transcendental. The smallest object of experience (for example, only pleasure or pain), that should be included in the general representation of self-consciousness, would immediately change the rational into an empirical psychology.
"I think" is therefore the only text of rational psychology, from which it must develop its whole system. It is manifest that this thought, when applied to an object (myself), can contain nothing but transcendental predicates thereof; because the least empirical predicate would destroy the purity of the science and its independence of all experience.
But we shall have to follow here the guidance of the categories,—only, as in the present case a thing, "I," as thinking being, is at first given, we shall—not indeed change the order of the categories as it stands in the table,—but begin at the category of substance, by which at the a thing a thing is represented and proceeds backwards through the series. The topic of the rational doctrine of the soul, from which everything else it may contain must be deduced, is accordingly as follows:
