Transcendental idealism is opposed to empirical idealism. It maintains that phenomena are representations merely, not things in themselves. Space and time are the sensuous forms of our intuitions. Empirical idealism, on the other hand, goes together with transcendental realism. It maintains that space and time are given as real in themselves, in independence of our sensibility. (Transcendental here, as in the phrase “transcendental ideality,”[1008] is exactly equivalent to transcendent.) But such a contention is inconsistent with the other main tenet of empirical idealism. For if our inner representations have to be taken as entirely distinct from their objects, they cannot yield assurance even of the existence of these objects. To the transcendental idealist no such difficulty is presented. His position naturally combines with empirical realism, or, as it may also be entitled, empirical dualism. Material bodies in space, being merely subjective representations, are immediately apprehended. The existence of matter can be established “without our requiring to issue out beyond our bare self-consciousness or to assume anything more than the certainty of the representations in us, i.e. of the cogito ergo sum.”[1009] Though the objects thus apprehended are outside one another in space, space itself exists only in us.

“Outer objects (bodies) are mere appearances, and are therefore nothing but a species of my representations, the objects of which are something only through these representations. Apart from them they are nothing. Thus outer things exist as well as I myself, and both, indeed, upon the immediate witness of my self-consciousness....”[1010]

The only difference is that the representation of the self belongs only to inner, while extended bodies also belong to outer sense. There is thus a dualism, but one that falls entirely within the field of consciousness, and which is therefore empirical, not transcendental. There is indeed a transcendental object which “in the transcendental sense may be outside us,”[1011] but it is unknown and is not in question. It ought not to be confused with our representations of matter and corporeal things.

From this point[1012] the argument becomes disjointed and repeats itself, and there is much to be said in support of the contention of Adickes that the remainder of the section is made up of a number of separate interpolations.[1013] First, Kant applies the conclusion established in the Postulates of Empirical Thought, viz. that reality is revealed only in sensation. As sensation is an element in all outer perception, perception affords immediate certainty of real existence, Kant next enters[1014] upon a eulogy of sceptical idealism as “a benefactor of human reason.” It brings home to us the utter impossibility of proving the existence of matter on the assumption that spatial objects are things in themselves, and so constrains us to justify the assertions which we are at every moment making. And such justification is, Kant here claims, only possible if we recognise that outer objects as mere representations are immediately known. In the next paragraph we find a sentence which, together with the above eulogistic estimate of the merits of idealism, shows how very far Kant, at the time of writing, was from feeling the need of differentiating his position from that of subjectivism. The sentence is this:

“We cannot be sentient of what is outside ourselves, but only of what is in ourselves, and the whole of our self-consciousness therefore yields nothing save merely our own determinations.”

It is probable, indeed, that the paragraph in which this occurs is of very early origin, prior to the development of the main body of the Analytic; for in the same paragraph we also find the assertion, utterly at variance with the teaching of the Analytic and with that of the first and third Paralogisms, that “the thinking ego” is known phenomenally as substance.[1015] We seem justified in concluding that the various manuscripts which have gone to form this section on the fourth Paralogism were written at an early date within the Critical period.

We may note, in passing, two sentences in which, as in that quoted above, a distinction between representations and their objects is recognised in wording if not in fact.

“All outer perception furnishes immediate proof of something actual in space, or rather is the actual itself. To this extent empirical realism is beyond question, i.e. there corresponds to our outer perceptions something actual in space.”[1016]

Again in A 377 the assertion occurs that “our outer senses, as regards the data from which experience can arise, have their actual corresponding objects in space.” Certainly these statements, when taken together with the other passages in this section, form a sufficiently strange combination of assertion and denial. Either there is a distinction between representation and its object or there is not; if the former, then objects in space are not merely representations; if the latter, then the “correspondence” is merely that of a thing with itself.[1017]

This refutation of idealism will not itself stand criticism. For two separate reasons it entirely fails to attain its professed end. In the first place, it refutes the position of Descartes only by virtually accepting the still more extreme position of Berkeley. Outer objects, Kant argues, are immediately known because they are ideas merely. There is no need for inference, because there is no transcendence of the domain of our inner consciousness. In other words, Kant refutes the problematic idealism of Descartes by means of the more subjective idealism of Berkeley. The “dogmatic” idealism of Berkeley in the form in which Kant here defines it,[1018] namely, as consisting in the assertion that the notion of an independent spatial object involves inherent contradictions, is part of his own position. For that reason he was bound to fail in his promise[1019] to refute such dogmatic idealism. Fortunately he never even attempts to do so. In the second place, Kant ignores the fact that he has himself adopted an “idealist” view of inner experience. Inner experience is not for him, as it was for Descartes, the immediate apprehension of genuine reality. As it is only appearance, the incorporation of outer experience within it, so far from establishing the reality of the objects of outer sense, must rather prove the direct contrary. No more is really established than Descartes himself invariably assumes, namely, the actual existence of mental representations of a corporeal world in space. Descartes’ further assertion that the world of things in themselves can be inferred to be material and spatial, Kant, of course, refuses to accept. On this latter point Kant is in essential agreement with Berkeley.