Notoriously, Kant offers several different formulations of this principle, the first of which runs as follows: “act only in accordance with that maxim through which you can at the same time will that it become a universal law” (4:421). (Again, cf. 5:19f[15]). Bvii, A834=B862); reason’s is that of unity. Immanuel Kant (1724-1804) is considered one of the giants of philosophy, of his age or any other. It is an excellent basis for my revision." [1] In addition, sound philosophical reasoning requires that reason gain knowledge of itself—a task that is begun, but not completed, in the first Critique (§1.4). Thus Kant proposes three questions that answer “all the interest of my reason”: “What can I know?” “What must I do?” and “What may I hope?” (A805=B833). The difficulty of judging what the categorical imperative requires, however, only arises if Kant has adequately justified it. 7 Is Practical Justification in Kant Ultimately Dogmatic? To gain this entitlement, they must be autonomous—that is, not dependent on an authority that itself refuses justification. So, Kant argues, we must postulate God’s existence, while a belief in immortality enables us to hope that we will come closer to virtue so as to be worthy of happiness. Kant’s approach to practical reason is compared and contrasted with some contemporary ideas about “practical rationality”. What, then, is the relation of metaphysics—or philosophical reasoning more generally—to those areas of human enquiry that do seem to generate certainty (geometry and mathematics) and the expansion of knowledge (science in general)? If I am free to step back from all inclinations, those inclinations do not provide a compelling reason to act in any particular way. When Kant speaks of the “unity of reason” in the first Critique, he means that reason gives “unity a priori through concepts to the understanding’s manifold cognitions” (A302/B359; cf. The Critique of Practical Reason contains two sections, the Doctrine of Elements, containing the Analytic of Pure Practical Reason and the Dialectic of Pure Practical Reason. Arguably, all three accounts fail in providing reasoned justification to one or another audience. By contrast, the claim that such unity does exist would represent a “constitutive principle,” the sort of “cosmological” knowledge claim that we cannot justify. (See Kant’s Philosophy of Mathematics [forthcoming].) Immanuel Kant Trans. O’Neill (2000) situates the Kantian account of reason against three alternatives, which she labels the instrumental, the communitarian, and the perfectionist. Someone who takes her particular tradition to define what beliefs and practices count as reasonable can have little to say to those who stand outside it. This unity must be a priori since it cannot be given through any set of experiences. So it is not conditioned by anything else—for instance, by a desire for happiness or merely subjective wishes. (5:21), A second possibility—in some respects, an inversion of the previous one—would be to disregard my own inclinations and submit to another’s dictates, or perhaps the laws and customs my community. 4; Guyer and Walker 1990; Kant’s Theory of Judgment, §§1.3, 1.4). So Kant says: it is requisite to reason’s lawgiving that it should need to presuppose only itself, because a rule is objectively and universally valid only when it holds without the contingent, subjective conditions that distinguish one rational being from another. Kant’s idea that reason has “interests,” or even “needs,” may seem strange, and is discussed by Kleingeld 1998a. [Dare to be wise!] This is his distinction between the “constitutive” and “regulative” use of ideas. Here, Kant is not primarily concerned with enlightenment as the activity or condition of an individual: rather as something that human beings must work towards together.