If, now, we take the above propositions—as they must be accepted as valid for all thinking beings in the system of rational psychology—in synthetical connection, and proceed, from the category of relation, with the proposition: “All thinking beings are, as such, substances,” backwards through the series, till the circle is completed; we come at last to their existence, of which, in this system of rational psychology, substances are held to be conscious, independently of external things; nay, it is asserted that, in relation to the permanence which is a necessary characteristic of substance, they can of themselves determine external things. It follows that idealism—at least problematical idealism, is perfectly unavoidable in this rationalistic system. And, if the existence of outward things is not held to be requisite to the determination of the existence of a substance in time, the existence of these outward things at all, is a gratuitous assumption which remains without the possibility of a proof.
But if we proceed analytically—the “I think” as a proposition containing in itself an existence as given, consequently modality being the principle—and dissect this proposition, in order to ascertain its content, and discover whether and how this Ego determines its existence in time and space without the aid of anything external; the propositions of rationalistic psychology would not begin with the conception of a thinking being, but with a reality, and the properties of a thinking being in general would be deduced from the mode in which this reality is cogitated, after everything empirical had been abstracted; as is shown in the following table:
1
I think,
2 3
as Subject, as simple Subject,
4
as identical Subject,
in every state of my thought.
Now, inasmuch as it is not determined in this second proposition, whether I can exist and be cogitated only as subject, and not also as a predicate of another being, the conception of a subject is here taken in a merely logical sense; and it remains undetermined, whether substance is to be cogitated under the conception or not. But in the third proposition, the absolute unity of apperception—the simple Ego in the representation to which all connection and separation, which constitute thought, relate, is of itself important; even although it presents us with no information about the constitution or subsistence of the subject. Apperception is something real, and the simplicity of its nature is given in the very fact of its possibility. Now in space there is nothing real that is at the same time simple; for points, which are the only simple things in space, are merely limits, but not constituent parts of space. From this follows the impossibility of a definition on the basis of materialism of the constitution of my Ego as a merely thinking subject. But, because my existence is considered in the first proposition as given, for it does not mean, “Every thinking being exists” (for this would be predicating of them absolute necessity), but only, “I exist thinking”; the proposition is quite empirical, and contains the determinability of my existence merely in relation to my representations in time. But as I require for this purpose something that is permanent, such as is not given in internal intuition; the mode of my existence, whether as substance or as accident, cannot be determined by means of this simple self-consciousness. Thus, if materialism is inadequate to explain the mode in which I exist, spiritualism is likewise as insufficient; and the conclusion is that we are utterly unable to attain to any knowledge of the constitution of the soul, in so far as relates to the possibility of its existence apart from external objects.
And, indeed, how should it be possible, merely by the aid of the unity of consciousness—which we cognize only for the reason that it is indispensable to the possibility of experience—to pass the bounds of experience (our existence in this life); and to extend our cognition to the nature of all thinking beings by means of the empirical—but in relation to every sort of intuition, perfectly undetermined—proposition, “I think”?
There does not then exist any rational psychology as a doctrine furnishing any addition to our knowledge of ourselves. It is nothing more than a discipline, which sets impassable limits to speculative reason in this region of thought, to prevent it, on the one hand, from throwing itself into the arms of a soulless materialism, and, on the other, from losing itself in the mazes of a baseless spiritualism. It teaches us to consider this refusal of our reason to give any satisfactory answer to questions which reach beyond the limits of this our human life, as a hint to abandon fruitless speculation; and to direct, to a practical use, our knowledge of ourselves—which, although applicable only to objects of experience, receives its principles from a higher source, and regulates its procedure as if our destiny reached far beyond the boundaries of experience and life.
From all this it is evident that rational psychology has its origin in a mere misunderstanding. The unity of consciousness, which lies at the basis of the categories, is considered to be an intuition of the subject as an object; and the category of substance is applied to the intuition. But this unity is nothing more than the unity in thought, by which no object is given; to which therefore the category of substance—which always presupposes a given intuition—cannot be applied. Consequently, the subject cannot be cognized. The subject of the categories cannot, therefore, for the very reason that it cogitates these, frame any conception of itself as an object of the categories; for, to cogitate these, it must lay at the foundation its own pure self-consciousness—the very thing that it wishes to explain and describe. In like manner, the subject, in which the representation of time has its basis, cannot determine, for this very reason, its own existence in time. Now, if the latter is impossible, the former, as an attempt to determine itself by means of the categories as a thinking being in general, is no less so.[47]
[47] The “I think” is, as has been already stated, an empirical proposition, and contains the proposition, “I exist.” But I cannot say, “Everything, which thinks, exists”; for in this case the property of thought would constitute all beings possessing it, necessary beings. Hence my existence cannot be considered as an inference from the proposition, “I think,” as Descartes maintained—because in this case the major premiss, “Everything, which thinks, exists,” must precede—but the two propositions are identical. The proposition, “I think,” expresses an undetermined empirical intuition, that perception (proving consequently that sensation, which must belong to sensibility, lies at the foundation of this proposition); but it precedes experience, whose province it is to determine an object of perception by means of the categories in relation to time; and existence in this proposition is not a category, as it does not apply to an undetermined given object, but only to one of which we have a conception, and about which we wish to know whether it does or does not exist, out of, and apart from this conception. An undetermined perception signifies here merely something real that has been given, only, however, to thought in general—but not as a phenomenon, nor as a thing in itself (noumenon), but only as something that really exists, and is designated as such in the proposition, “I think.” For it must be remarked that, when I call the proposition, “I think,” an empirical proposition, I do not thereby mean that the Ego in the proposition is an empirical representation; on the contrary, it is purely intellectual, because it belongs to thought in general. But without some empirical representation, which presents to the mind material for thought, the mental act, “I think,” would not take place; and the empirical is only the condition of the application or employment of the pure intellectual faculty.
Thus, then, appears the vanity of the hope of establishing a cognition which is to extend its rule beyond the limits of experience—a cognition which is one of the highest interests of humanity; and thus is proved the futility of the attempt of speculative philosophy in this region of thought. But, in this interest of thought, the severity of criticism has rendered to reason a not unimportant service, by the demonstration of the impossibility of making any dogmatical affirmation concerning an object of experience beyond the boundaries of experience. She has thus fortified reason against all affirmations of the contrary. Now, this can be accomplished in only two ways. Either our proposition must be proved apodeictically; or, if this is unsuccessful, the sources of this inability must be sought for, and, if these are discovered to exist in the natural and necessary limitation of our reason, our opponents must submit to the same law of renunciation and refrain from advancing claims to dogmatic assertion.
But the right, say rather the necessity to admit a future life, upon principles of the practical conjoined with the speculative use of reason, has lost nothing by this renunciation; for the merely speculative proof has never had any influence upon the common reason of men. It stands upon the point of a hair, so that even the schools have been able to preserve it from falling only by incessantly discussing it and spinning it like a top; and even in their eyes it has never
