In his preface to the Critique of Pure Reason, Kant sketches his vision of philosophy’s task after the transcendental turn. For the purposes of this essay, I will limit my discussion to metaphysics, which is also the subject of this first Critique. Kant famously calls metaphysics “the queen of all the sciences” (A viii). He traces a path between the dogmatism (despotic tyranny) and skepticism (complete anarchy) that he says have characterized most previous metaphysics. Kant notes that Locke had attempted but failed to “put an end to all these controversies … through a certain physiology of the human understanding” (A ix). Kant puts this point more strongly still in the preface to the second edition, where he compares the path of metaphysics to other sciences. Logic has “travelled the secure course of a science” since Aristotle (B vii). The path of logic has been relatively easy, though, since it “has to do with nothing further than itself and its own form” (B ix). Metaphysics, by contrast, “has to deal with objects [Objecte] too,” and therefore “logic as a propaedeutic constitutes only the outer courtyard, as it were, to the sciences” (B ix).
Kant’s task is to put metaphysics on the same “secure course of a science” as mathematics and physics. The task of the philosopher is to undertake this kind of scientific inquiry with respect to reason itself. What does this path of metaphysics as science consist in? Well, Kant says, up to now “it has been assumed that all our cognition must conform to the objects.” Since this has “come to nothing,” Kant tells us, “let us once try whether we do not get farther with the problems of metaphysics by assuming that the objects must conform to our cognition” (B xvi). Here he makes an analogy with Copernicus. Before the Copernican Revolution, celestial phenomena were explained as dependent on the motion of heavenly bodies alone, since the Earth was stationary; after Copernicus, these same observed phenomena were explained as dependent on both the motion of heavenly bodies and the motion of the Earth. Kant proposes something analogous: before him, the phenomena of human experience were explained as dependent on the sensible world, with the mind uninvolved in structuring these phenomena; Kant argues, by contrast, that the phenomena of human experience are structured by both sensory data and a basic structure supplied by the human mind. Instead of a sensible world orbiting around a stationary mind, both the mind and objects are involved in structuring the phenomena of human experience. “This experiment,” Kant says, “promises to metaphysics the secure course of a science,” not least because it borrows its structure from the very revolution that also set astronomy on the secure course of a science. Kant is thus “undertaking an entire revolution [in metaphysics] according to the example of the geometers and natural scientists” (B xxii).
Thus, Kant’s a priori metaphysics paradoxically occurs only after the fact of modern science. Descartes had attempted to provide a secure foundation through reflection from first principles, foundations that are as certain for science as for philosophy. Hume’s skepticism had attempted to undermine these foundations, a move that troubled Kant deeply. Kant did not go on to offer a defense or elaboration of Cartesian metaphysics. Instead, he shifted the question. Now, the task of metaphysics is not to provide secure first foundations for science. Instead, it takes the facts of science (and especially Newtonian physics) as true, and then asks for the conditions of possibility of these scientific facts. (The truth of these facts, it seems, is derived mostly from their success in practice, and specifically through the great advances in technology and industry around Kant’s time.) Kant is thus doing metaphysics in the Aristotelian sense: he investigates the structure of a priori reason after the fact (meta) of physics.
The task of the philosopher is not to prove the truth of science from first foundations — that, in a way, takes care of itself through practise. What, then, is the use of metaphysics? Is it “only of negative utility, teaching us never to venture with speculative reason beyond the boundaries of experience” (B xxv)? Indeed, Kant says, this is “its first usefulness” (B xxv). But Kant’s ambitions are much greater. Namely, he thinks that his kind of metaphysics will allow us to have our cake and eat it, so to say: we can secure modern science (and ensure ourselves of its benefit) while preserving space for human freedom. How so? Well, this move relies on Kant’s distinction between the realm of phenomena or appearances on the one hand and things-in-themselves on the other hand. In Kant’s elaboration of the conditions of possibility, he identifies space and time as “conditions of the existence of the things as appearances”; in other words, “we have no concepts of the understanding and hence no elements for the cognition of things except insofar as an intuition can be given corresponding to these concepts” (B xxvi). On the face of it, this constrains human freedom by placing strict limits on what it is possible to think. But no! Kant says that “even if we cannot cognize [some] objects as things in themselves, we at least must be able to think them as things in themselves.” The realm of appearances is structured by certain conditions of possibility that structure our thinking — hence, in this realm there is little in the way of human freedom. There is another realm, though, of things in themselves. How do we know anything about this realm, the proper domain of metaphysics? Well, to cognize such an object “it is required that I be able to prove its possibility,” namely by following from the realm of appearances. But “I can think whatever I like, as long as I do not contradict myself” (B xxvi).
This kind of bifurcation of metaphysics and hence of thinking might seem superficial or inconsequential. But Kant thinks this is his major achievement, ultimately. He thinks that distinguishing between appearances and things in themselves (where “the principle of causality applies only to things taken in the first sense … while things in the second meaning are not subject to it”) allows the will to be thought of as both not free (subject to the conditions of possibility he has established) and free. As he writes: “just the same will is thought of in the appearance … as necessarily subject to the law of nature and to this extent not free, while yet on the other hand it is thought of as belonging to a thing in itself not subject to that law, and hence free” (B xxviii). This is monumental. The consequences of limiting thinking (as dogmatic metaphysics would have us do) are devastating: “freedom and with it morality … would have to give way to the mechanism of nature” (B xxix). Kant saves us from this. This is why he thinks his “legacy of a systematic metaphysics, constructed according to the critique of pure reason, … is still a gift deserving of no small respect” (B xxx). He preserves freedom from the threat of science in its guise as dogmatic metaphysics; and yet in so doing, “everything yet remains in the same advantageous state as it was before concerning … the utility that the world has so far drawn from the doctrines of pure reason” (B xxxii). In elaborating metaphysics through the critique of reason, the “speculative philosopher … remains the exclusive trustee of a science that is useful to the public even without their knowledge” (B xxxiv).
So much for the positive legacy of this metaphysics; now one last note on what a philosopher should offer to the public through his work. What Kant prizes above all else are certainty and clarity. To the latter point, Kant distinguishes between “discursive (logical) clarity, through concepts, but then also intuitive (aesthetic) clarity, through intuitions, that is, through examples” (A xvii). The former is what Kant claims to have achieved; the latter, he disavows as “necessary only for a popular aim,” which his work would never be. Furthermore, such aesthetic clarity is ultimately unhelpful for the reader, Kant thinks, since “all their bright colors paint over and make unrecognizable the articulation or structure of the system, which yet matters most when it comes to judging its unity and soundness” (A xix). In the preface to the second edition, he adds approvingly that this kind of “coloring in” has been undertaken by many others. This is a task he will not himself undertake, in the first place because he does not have the knack and second because he grows old. He praises “courageous and clear minds” who have publicly expounded on Kant’s Critique, saying that
To these deserving men, who combine well-groundedness of insight so fortunately with the talent for a lucid presentation (something I am conscious of not having myself), I leave it to complete my treatment, which is perhaps defective here and there in this latter regard. … For my own part, from now on I cannot let myself become involved in controversies, … since during these labors I have come to be rather advanced in age. … Meanwhile, if a theory is really durable, then in time the effect of action and reaction, which at first seemed to threaten it with great danger, will serve only to polish away its rough spots, and if men of impartiality, insight, and true popularity make it their business to do this, then in a short time they will produce even the required elegance. (B xliii)
I have outlined three things that Kant has bequeathed to philosophers after him. First, that philosophy should properly come after the sciences; in other words, philosophy takes and ought to take the achievements of the sciences as facts and secure their foundations. Second, that as much as this may be the first task of metaphysics, the philosopher should set his sights much higher than being the mere handmaiden of science. Indeed, what philosophy ultimately aims for is to secure the foundations of human freedom; it is in reconciling this freedom with science that philosophy can offer something of positive utility to the world. Third and finally, that in completing this task the philosopher should aim for the twin characteristics of certainty and logical clarity, but to some extent should disregard the demands of intuitive or aesthetic clarity.
I respect the first of these, deeply admire the second, and lament the third. (Why must some philosophers be so hard to read? Even Kant seems to admit it as a feeling, if an excusable one, but I think the shadow cast by his great achievements led to the unfortunate emulation of his style, which is by no means a necessary part of the philosopher’s task.) The achievements of science are not to be diminished. I think today we might be less interested in the first point but that is simply because Kant has been so enormously successful; as scientists and scholars, we feel no risk of drifting back to pre-modern dogmatism. Even if we criticize science, it is against the “background noise” of a secure, hugely successful enterprise. Yet it is refreshing to read this exhortation today and remember that even in our critiques we are really co-laborers in the broad project of science. But this project of science is emphatically not an end in itself. Here I am reminded of a famous autobiographical passage of Kant’s from his Observations on the Feeling of the Beautiful and Sublime:
I myself am a researcher by inclination. I feel the entire thirst for cognition and the eager restlessness to proceed further in it, as well as the satisfaction at every acquisition. There was a time when I believed this alone could constitute the honor of humankind, and I despised the rabble who knows nothing. Rousseau has set me right. This blinding prejudice vanishes, I learn to honor human beings, and I would feel by far less useful than the common labourer if I did not believe that this consideration [i.e. “what I am doing”] could impart a value to all others in order to establish the rights of humanity. (Prussian Academy edition 20:44)
Kant began as an eager scientist, and the first Critique remains animated by the firm admiration of the achievements of science and a conviction that philosophy must come after these achievements (meta ta physika). Yet Kant realizes that this is ultimately an empty aim. The project of the Critique is in the end useful only insofar as it secures the establishment of the rights of mankind. Kant’s spirit is the spirit of the Enlightenment: firm in its support both of science and of political liberties and civil rights. This is the legacy we are still grappling with today, and we would do far worse than to carry on Kant’s spirit (as long as we shake off his dreadful Latinate writing style!)