What does Athens have to do with Prussia? Perhaps more than one might think. Having spent a semester with the Critique of Pure Reason, it seems to me Platonists, Aristotelians, and friends of the Forms generally may have a friend in the sage of Königsberg. An unexpected friendship to be sure insofar as Kant would consider Plato and Aristotle ‘transcendental realists.’ Plato and Aristotle think that knowledge is a question about how concepts apply to objects. Kant’s doctrine of ‘transcendental idealism’ famously reverses this equation. Epistemology and metaphysics, he argues, ought to examine how objects are adequate to the knower’s categories and concepts. Metaphysical knowledge, knowledge of synthetic a priori propositions, is supposedly more intelligible from this standpoint, since it is easier to talk about the conditions of any possible experience for a knowing subject than discussing objects in themselves apart from the experience.
Yet this admittedly rocky start shouldn’t deter us, for Platonists and Kantians are united in asking what is perhaps philosophy’s most important question. How is knowledge of the world possible? Or, even more basic, why is the world intelligible to me in the first place? Despite their different approaches, their query is the same. Platonists tend to analyze the conditions of the possibility of an intelligible world. That is, they examine the ground for objects manifesting themselves in such a way that reason can interact with them. Forms are almost always a crucial part of this answer. Kantians, on the other hand, examine the subject for whom an intelligible world exists.
Despite taking different approaches to the question of intelligibility, I see no reason why Platonists should reject Kant’s insights regarding the subject for whom there is an intelligible world. This is especially true when talking about the B Deduction in the Critique of Pure Reason, which, by any measure, is a masterpiece of transcendental argumentation. Take §15, where Kant introduces the concept of combination. Most of the argument in the TD seems premised on the phenomenological insight that a combination of representations cannot be explained by passive sensibility. A Platonist or Aristotelian would reject Kant’s characterization of the senses as entirely passive, but the point is nonetheless a good one for refuting naïve empiricists. If there is a red square table in front of me, Kant wants me to recognize that nothing about redness or squareness explains their connection in this table. The connection or combination of representations is ab extra. If the senses are passive, Kant thinks this ab extra must be the result the understanding’s “self-activity.” “Combination (conjunctio) of a manifold in general can never come to us through the senses… for it is an act of the spontaneity (of reason).”
This allows Kant to conclude that the understanding must introduce the concept of unity into its representations. There is nothing about redness or squareness that explains their unity in this table. But the representation of this red square table is a unified one for me. How is this possible? Not solely on account of the senses. Rather the self or the understanding must introduce the concept of unity into its representations. “The representation of this unity cannot, therefore, arise from the combination; rather by being added to the combination of the manifold, it first makes the concept of combination possible.” Combination of representations in experience, Kant argues, is only possible if the self introduces unity into its representations. A purely passive subject, whose understanding did not function in this way, would perceive the world in Humean bundles, as loose conglomerations of impressions that fail to inhere in one thing.
If cthe ombination of representations is only possible because the understanding introduces unity into its representations, we must grasp its original contribution in more detail. This takes us to what, in my opinion, is the most persuasive part of the TD and the Critique in general. In §16 Kant argues that every representable perception must in principle be thinkable. He writes:
The I think must be able to accompany all my representations; for otherwise something would be represented in me that could not be thought at all, which is as much to say that the representation would either be impossible or else at least would be nothing for me.
By this I understand him to be saying that there is no conceptual difference between an unthinkable or unintelligible representation and an unrepresentable one (i.e. what is nothing for me). I can represent something if and only if I can think it. The I think must be able to accompany any representation at least in principle. But this is to say that I can only represent x if I can also say ‘I think x.” Intelligibility (or thinkability) and representability are reciprocally related concepts. Any representation, therefore, even the most basic sense perception, must be thinkable or intelligible.
Kant moves from the conceptual unity of thinkability/intelligibility and representability to a rather remarkable claim about all representations as such. A good Aristotelian in this respect, Kant infers that if all actual representations must in principle be thinkable or accompanied by the I think in order to be something for me, then any potential representation “must yet necessarily be in accord with the condition under which alone they can stand together in universal self-consciousness.” Here Kant is making an important claim about how representations as such must be in order for them to be given to a single self-consciousness (the same I think). Representations, even if only potentially related to consciousness, must yet be in accord with whatever conditions would allow them to be actually given to that consciousness. Kant has moved from the claim that all representations of intuition are necessarily intelligible to one that says that if there is any representation in me, even a representation of which I am not currently conscious, it must still be such that it can be totally given to me, to my consciousness. In other words, representations are possible for me if and only if they are representable or intelligible in themselves. This is the ground of their potentially being given to me at all.
This last claim is one that every Platonist ought to embrace. Even if Kant’s Copernican philosophy is mostly revolutionary, in this respect he is a reactionary. For Kant is claiming, alongside the ancients (and against the rationalists and empiricists before him), that representations, sense-perceptions, or impressions of whatever kind must in principle be intelligible to consciousness. They are per se the kinds of things that can be given to consciousness. Were this not the case, representations would be nothing. But is this not similar to saying that Being, insofar as it is actually or potentially given to mind, is per se thinkable?