Recently somebody on Twitter (using the handle @robotsneedpoems) complained to me about the Critique of Pure Reason:

It’s crazy to me how confident K[ant] is in his ability to discern discrete cognitive faculties just by reasoning them out. He keeps plowing ahead, constructing a mind-numbingly complex account out of more or less thin air.

I suspect this is a common reading experience. Kant seems to start out in a quite parsimonious way by distinguishing just two cognitive powers, sensibility and the understanding. But before long the understanding has fallen apart into the understanding, the power of judgement and reason; at least two kinds of imagination have been added; and who knows whether the ‘hidden art’ that gives us the schematised versions of the categories is yet some further cognitive power? And so we are now looking at at least six, and maybe more, cognitive powers, and the entire theoretical edifice is starting to seem both baroque and unmotivated.

How many cognitive powers are there, according to Kant? Two? Six? I want to suggest that there is an important sense in which this question is misleading; a sense in which asking this question is to miss what is most central and interesting about Kant’s conception of cognition. For what is most central and interesting is the idea that our cognitive powers form a unity, a functional, goal-directed unity; and that while it will be necessary, when doing philosophy, to distinguish different powers or faculties, we should never lose sight of the fact that those power are intelligible only within the context of the essential unity of our cognition. And so the answer to the question ‘how many cognitive powers are there?’ must be in some sense ‘one’, and in some sense ‘as many as are useful in the attempt to understand our own understanding’. We do not ‘discover’ that the understanding actually consists of three powers, the understanding, the power of judgment, and reason. Rather, it turns out to be philosophically useful to distinguish between the grasp of concepts, the bringing together of concepts in judgments, and the bringing together of judgments in arguments. But none of these abilities would, for Kant, make sense independently of the others. It is not just that arguments require judgments and judgments require concepts, which most philosophers would agree with; it is also that concepts only make sense as the constituents of judgments, and that judging only makes sense within the greater project of linking judgments together into a single coherent body of knowledge. All of the faculties presuppose all of the others. Kant is not doing armchair cognitive psychology and discovering lots of hitherto unknown faculties. He is merely working out what it means to be finite cognitive agent; what it means to be the kind of thinker who strives for objective knowledge by applying general concepts to objects that are given to them.

Perhaps it is best to illustrate the fundamental role of unity within Kant’s thought by looking at his famous remark that ties together sensibility (through which objects are given to us, something English Kant calls intuition and original Kant calls Anschauung) and the understanding (which is the faculty of applying concepts). Kant writes:

Thoughts without content are empty, intuitions without concepts are blind.

This remark clearly brings the two faculties together in a strong way: each is useless (’empty’ or ‘blind’) without the other. But if that is all we say, we are still underestimating how close the tie is between sensibility and the understanding. For it suggests that we can at least understand the nature of sensibility and the understanding apart from their relation to each other. But recall that for Kant our cognitive powers form a functional unity; they are essentially defined by their aim, which is objectively valid cognition. Now without sensibility, the understanding cannot come into contact with any objects. Without the understanding, sensibility cannot give rise to cognition. So neither can reach the aim that is essential to them without the other. In fact, and it is easy to overlook this, while sensibility is defined as a power that brings us into contact with objects, it cannot do even this much without the contribution of the understanding; for an object is essentially something that falls under the categories of the understanding. And vice versa the understanding, which is supposed to apply concepts, cannot do that in any serious sense of the term if nothing is given to it in sensibility. So even these two cognitive faculties, the distinction between which is foundational for the entire story of the Critique, are not (as James Conant would phrase it) ‘self-standingly intelligible’. Our understanding of each presupposes the other.

Kant’s Critique can only be understood by keeping in mind that his subject is the finite knower, someone whose cognition has both an active and a passive pole; passive in that we are affected by objects, active in that we judge and reason. These poles cannot be understood apart from each other, and they also cannot be understood apart from their telos, their aim, namely, unified knowledge of the world. Everything Kant says about our cognitive faculties is an attempt to think through this basic situation. We first distinguish between sensibility and the understanding in order to talk about the passive and the active pole of cognition. We then realise that we must be able to actively work with what has been passively given to us, and we call the power to do this the imagination. And so on.

Behind all the distinctions that Kant makes, there always lies a fundamental unity. What is transcendental idealism? I think the following would be a good one sentence attempt to define it:

The unity of the subject, the unity of the world, and the unity that is the goal of inquiry, are one and the same unity; one and the same in the very strong sense that each of them is intelligible only when the other two are thought along with it.

This was and remains an absolutely radical idea. It undermines, among other things, the Cartesian claim that we can grasp the unity of the self apart from any grasp of the world; and the metaphysical realist’s claim that one can grasp the unity of the world independently of a grasp of our modes of inquiry. I think Kant is absolutely right. And it is because of that that I think the Critique of Pure Reason remains one of the most important philosophical texts to study; and also because of that that I am increasingly willing to call myself a transcendental idealist.