Transcendental idealism is otherwise. Reality as perceived by the mind is ideal in the sense that things appear in experience to be other than they are in themselves, but this ideality is the effect of application of intuition and the categories to realities that must exist prior to thought in order to become (when modified by the cognitive faculty) objects of experience. Far from proving that external objects do not exist or that their existence is only possible, not actual or necessary, transcendental idealism requires external objects to give experience content at all. Keep that in mind while pondering the Theorem in the Refutation:
The mere, but empirically determined, consciousness of my own existence proves the existence of objects in space outside me.Consciousness of my existence proves that external objects exist because my consciousness of my existence would not come about without the existence of external objects:
Hence determination of my existence in time is possible only through the existence of actual things that I perceive outside me.Several problems: idealism is not refuted by showing that I present objects as being outside myself (in space instead of as part of my inner experience), but by showing that the realities to which these presentations correspond are actually something outside myself. Because "outside" and "external" are spatial terms, applying only to objects in experience, it is unclear how anything can be ontologically distinct from myself, and certainly is seems impossible, in transcendental idealism, for an external object to be ontologically external. Also, if inner experience cannot be determined without juxtaposition to outer experience, inner experience itself is contingent on outer experience, and, further, it is determinable only negatively. Inner experience can be described only as "whatever is not outer experience," with no inherent features of its own. This view seems dangerously close to denying that a self exists at all, for its experience of itself (inner experience) is nothing more than a negation. If inner experience cannot be determined at all beyond such a negation, it is experience of a non-entity. It would be awfully depressing not to be anything.
The Proof of the Theorem starts off on a bad foot:
I am conscious of my existence as determined in time. All time determination presupposes something permanent in perception. But this permanent something cannot be something within me, precisely because my existence can be determined in time only by this permanent something. Therefore perception of this permanent something is possible only through a thing outside me and not through mere presentation of a thing outside me.Nothing objectionable is present in that passage until the last sentence, which actually contradicts the Critique's limitation of knowledge to the world of phenomena. Going through the argument: Inner intuition is organized temporally. So far, so good; and if anyone objects at this point, he must either leave Kant to the Kantians or read the Transcendental Aesthetic again. Temporal organization is possible only on the presupposition that a permanent "time" exists against which all temporal relations are compared. Again, as long as the Kantian conception of time is assumed at the outset (and, again, anyone who disagrees probably just disagrees with Kant and sees no efficacy of this Refutation of Idealism anyway, for it is, for him, nothing but a bolstering of a diseased structure of mistaken philosophy), this seems true. Moving on, the permanent thing giving substance (forgive the word!) to sequentiality and simultaneity cannot be in inner experience itself, for the coherence of that experience is itself contingent on the existence of the permanent thing. Thus the permanent thing cannot be the self. Now Kant trips over a confusion of levels: the permanent thing through which inner intuition gains its coherence must be an actually existing thing outside the self, not a mere presentation of permanence. Permanence is, however, a part of the concept of substance; up until this Refutation, I would have thought Kant perfectly committed to the idea that the presentation of permanence is that which makes inner experience possible. The operation would be something like this: the self, whatever it is, includes as part of its reality-interpreting function a presentation of permanence. This permanence is the result of the mind's operation on raw experience, not an ontologically independent permanence that the mind perceives. Having manufactured this permanence in its conception of reality, the mind now has the material to begin presenting the self to itself, as inner experience. Instead of taking that reasonable course, Kant declares that inner experience must be juxtaposed against an actually existing permanence that the mind is somehow able to perceive without having made it an aspect of presentation. What is that actual permanence but a noumenal reality, though? If presentation, then phenomenon; if not presentation, then noumenon.
The slip from phenomenal to noumenal conceals the question-begging inherent in a statement like "There are things actually outside me because I am conscious of things outside me." That statement makes sense if the consciousness of external objects includes consciousness of their actual externality, not merely consciousness that they are presented as being outside me. But consciousness in transcendental idealism is always about presentations, so that the statement collapses into the obvious fallacious "There are things actually outside me because I think them as outside me." Be careful, Immanuel; such thought makes the ontological argument work.
A footnote to Comment I to the Proof is also fraught with impermissible assumptions:
In the preceding theorem, the direct consciousness of the existence of external things is not presupposed but proved, whether or not we have insight into the possibility of this consciousness. The question concerning that possibility would be whether we have only an inner sense, and no outer sense but merely outer imagination. Clearly, however, in order for us even to imagine something - i.e., exhibit it to sense in intuition - as external, we must already have an outer sense, and must thereby distinguish directly the mere receptivity of an outer intuition from the spontaneity that characterizes all imagining. For if even outer sense were merely imagined, this would annul our very power of intuition which is to be determined by the imagination.Levels-confusion abounds in this footnote. The idealist argument against which Kant launches this footnote is that what is called "outer sense" may merely be an aspect of inner sense. Inner sense would be divided between "Things I present as part of inner sense belonging to me" and "Things I present as part of inner sense belonging to things other than me." That things are presented in two different ways (I and other-than-I) does not imply ontological distinctness between them. "Outer imagination" would be the faculty of presenting at least a part of inner sense as other-than-I, although, as inner sense, it would properly belong to the self and to nothing outside the self. Kant's response to that idea is shrouded in an obscure locution, but he seems to claim that even outer imagination assumes the existence of outer sense, which must be distinguishable from inner sense and apply to a different set of objects entirely. For the mind to imagine something as outer, it must at least be able to think externality; the idea of externality could not arise except if there were an independent faculty (outer sense) capable of receiving data about actually external objects and functioning as the receiver and interpreter of that kind of data. Against the idealist theory that inner sense is bifurcated between inner-sense-of-me and inner-sense-of-not-me, Kant argues that outer sense is a sense in its own right, not merely an artificial modification of inner sense, and that the objects of outer sense are always different from the single object ("I") of inner sense.
Far from clearing things up, that explanation assumes away the problem. Granted there is something properly called the "outer sense," how exactly does that sense operate any differently from "outer imagination," and why does the existence of outer imagination as an activity of the self assume that outer sense must exist and be about independent realities? I can only imagine something if I could have intuition of it; in other words, imagination is only possible on the assumption of possible intuition. It does not follow that I must have an actual outer sense capable of perceiving things actually outside me in order to imagine things as being outside myself. That "outer sense," whatever it is, is presented as being a receptivity (and thus presented phenomenally as being a faculty for taking in data from external objects and organizing those data into a coherent outer experience) does not mean it is actually a receptivity instead of a spontaneity. Certainly something must give experience content, unless intuition is capable of creating content from itself (which would make it intellectual intuition), so that something must exist besides the self which intuits, in order to provide the raw material for the intuition the self has of other things. Pinning down just what intuition arises from external things and what intuition arises from the self is a tricky business, though, and that is precisely what Cartesian idealism was all about. If intellectual intuition is to be avoided (and that massive issue requires more discussion that I can presently give it), some aspects of experience must be caused by something other than the mind's spontaneity. That the objects of outer sense would correspond precisely with those external causes would be convenient, a helpful confirmation of the correctness of transcendental idealism and empirical realism, but, alas, nothing about the nature of outer sense seems to bear indicia of actual externality. Kant recognizes that not all experience actually arises from external causes:
It does not follow, from the fact that the existence of external objects is required for the possibility of a determinate consciousness of ourselves, that every intuitive presentation of external things implies also these things' existence; for the presentation may very well be (as it is in dreams as well as in madness) the mere effect of the imagination.but fails to understand how difficult it is to tell whether a specific experience has an internal or external cause:
Whether this or that supposed experience is not perhaps a mere imagining must be ascertained by reference to its particular determination and by holding it up to the criteria of all actual experience.All actual experience may be imagined. What then?
An an aside: is the self presented as an external object when it is intuited? "Inner sense" is not really pure awareness of the self, but awareness of the self as intuited in time. Thus the self is altered even when it is conscious of its own existence. Therefore, even inner sense is a presentation of something other than the noumenal self, something not self-identical. That ought to be disturbing for Kant. If the self is presented as something not identical to itself, it is presented as if it were an external object, with the attached proviso "but this is really the self's inner experience." If presentation corresponds to reality, the self as intuited in time is an external object to the real self. This is an awfully unfortunate conclusion.
Kant avoids the intuition problem by denying it:
The consciousness that I have of myself in the presentation I is not an intuition at all, but is a merely intellectual presentation of a thinking subject's self-activity.I don't see how this is anything other than a reliance on intellectual intuition, for the very phrase "intellectual presentation" indicates the mind's non-empirical presentation of its own activity. Despite Kant's saying that this consciousness is not an intuition, it is a presentation and must, therefore, be presented to the mind somehow, i.e., through some intuition. How else is the mind to receive a presentation but through intuition? If the presentation "I" does not involve intuition, not even inner intuition, I would contend, following Kant's own argument throughout the First Critique, that it is entirely empty of content. Being empty of content, it is a mere thought-entity, and "I" is an empty word to the extent it refers to a thing divorced from intuition. Thus my previous point stands: "inner sense" is an intuition of something not precisely identical with "I".
Working from that aside, does not the Refutation of Idealism lead to skepticism about the existence of the self? Inner sense and its temporally-determined states are impossible without the existence of an actual external permanence against which the self and its successive states can be measured. By understanding the self in opposition to the external, the "I" as understood in itself becomes nothing more than what can be understood without such an opposition, but it ends up becoming nothing. Inner sense as the perception of the self as a quasi-external object allows consciousness to jibe with transcendental idealism's principle that only what is subject to cognition's forms can be experience for us. "I" as self-awareness without intuition becomes a single letter signifying no real object. The "I" is known only through a distinction between external and internal objects that holds only for experience. If this distinction were ontological, the "I" might survive, but as it is, the "I" is a mere artifact of empirical intuition! In different words: if the "I" depends for its existence on external realities, but those realities are external in only an ideal sense, the "I" has merely ideal existence, and no metaphysical existence. The Refutation has taken many victims in its broad sweep.
What is the title of this post all about, exactly? It's about my suggestion that Kant's cure for idealism was worse than the disease, and that a better solution to the problem is to deny that it is a problem for transcendental idealism. The whole Critique is an exercise in showing how incoherent metaphysics is. Idealism is a question about the metaphysical relations between subjects and objects; to that extent, idealism is nonsense. Objects do not exist except for minds, and what those things are in themselves is unknowable, because the mind can know only what it has made an object of knowledge. Reality only matters insofar as it is for minds; therefore, the very question about what things are like in themselves is meaningless. To those who believe the chasm between reality and perception is major philosophical problem, this solution is not satisfactory. But, following Kant, if that chasm cannot be bridged, and need not be bridged in order to give order, coherence, and objectivity to experience, then the problem diminishes in relevance to nothing. Where knowledge is impossible, ignorance is no evil. That acceptance is the true cure for idealism.