Thanks to David A. Schmidt and Elizabeth S. Radcliffe.

1 Kant, Immanuel, Groundwork of the Metaphysics of Morals, trans. and ed. Gregor, Mary (Cambridge: Cambridge University Press, 1997), 15/4: 402Google Scholar. Unless otherwise indicated, all subsequent references to the Groundwork are to this edition.

2 See Guyer, Paul, “The Derivation of the Categorical Imperative: Kant’s Correction for a Fatal Flaw,” The Harvard Review of Philosophy 10 (2002): 64-80CrossRefGoogle Scholar. See also: Allison, Henry E., Kant’s Theory of Freedom (Cambridge: Cambridge University Press, 1990), 212-3CrossRefGoogle Scholar; Allison, Henry E., Idealism and Freedom (Cambridge: Cambridge University Press, 1996), 152-4CrossRefGoogle Scholar; Kitcher, Patricia, “Kant’s Argument for the Categorical Imperative,” Noûs 38 (2004): 555-84CrossRefGoogle Scholar; and Rickless, Samuel C., “From the Good Will to the Formula of Universal Law,” Philosophy and Phenomenological Research 68 (2004): 554-77CrossRefGoogle Scholar.

3 Guyer’s critique and attempted correction of Kant’s derivation, which emphasizes “humanity” as an “objective end” of reason, will be discussed below. For criticism of Allison’s attempts to patch the derivation by invoking the idea of “transcendental freedom” see Mariña, Jacqueline, “Kant’s Derivation of the Formula of the Categorical Imperative: How to Get it Right,” Kant-Studien 89 (1998): 167-78CrossRefGoogle Scholar; see also Kerstein, Samuel J., Kant’s Search for the Supreme Principle of Morality (Cambridge: Cambridge University Press, 2002), 33-45CrossRefGoogle Scholar.

Some who suggest that the argument of Kant’s derivation can be patched by invoking “ought implies can” suppose that, by such a principle, a maxim upon which we all cannot act is one upon which we all ought not act. Hence, as the formula of universal law says, we ought not act on any maxim that cannot become, or that cannot be willed to become, a universal law (see Rickless, esp. 572). But this line of thinking commits a fallacy of misplaced negation. From “ought implies can” we get “cannot implies not ought.” We get the result that any way we all cannot act is a way we are all not obligated to act. And this is weaker than Kant’s formula of universal law. What would be needed in place of “ought implies can” is a principle more like “may implies can” (see Kitcher, 576). By this principle, cannot implies may not; that is, ought not. So a maxim upon which we all cannot act would be one upon which we all may not act, as the formula of universal law seems to say. But Kant would not have endorsed “may implies can.” For this principle would also obligate us not to do the impossible. Drawing circles with corners would be contrary to duty, for example. So for this reason it seems that “may implies can” cannot be inserted into the argument of Kant’s derivation as a stop-gap premise.

4 Potter calls this argument “unusual and not very convincing.” See Potter, Nelson, “The Argument of Kant’s Groundwork, Chapter 1,” in Guyer, Paul, ed., Kant’s Groundwork of the Metaphysics of Morals, Critical Essays (Lanham, NJ: Rowman and Littlefield, 1998), 29-49Google Scholar, at 37.

5 “In the natural constitution of an organized being, that is, one constituted purposively for life, we assume as a principle that there will be found in it no instrument for some end other than what is also most appropriate to that end and best adapted to it” (Groundwork, 8/4: 395).

6 Kant appears to have assigned a plurality of interests to reason. These include a speculative and a practical interest. See Immanuel Kant, Critique of Pure Reason, trans. and ed. Paul Guyer and Allen W. Wood [hereafter, Pure Reason] (Cambridge: Cambridge University Press, 1998), A466/B494, A797/B825; and see Immanuel Kant, Critique of Practical Reason, trans. and ed. Mary Gregor [hereafter, Practical Reason] (Cambridge: Cambridge University Press, 1997), 100-101/5: 119-20.

7 Korsgaard, for example, provides an interpretation of Kant’s formula of universal law that makes “practical contradiction,” or inconsistency between means and ends, the basis for moral judgment. The idea is that for wrong actions their maxims’ becoming universal laws would make the ends for which these actions are chosen impossible to achieve. See Korsgaard, Christine M., Creating the Kingdom of Ends (Cambridge, MA: Cambridge University Press, 1996), 77-105CrossRefGoogle Scholar.

8 Pure Reason, Bxx, Bxxiii-xxiv, A326/B382-3, A416-17/B443-5.

9 See ibid., A651/B679, A647/B675, A664-6/B692-4; and see Practical Reason, where Kant mentions “the undeniable need of human reason, which finds complete satisfaction only in a complete systematic unity of its cognitions” (77/5:91).

10 In Groundwork Kant talks about the rational being’s membership in an “intelligible world,” the laws of which, being independent of nature, are grounded in reason (57/4:452). In Practical Reason he writes that the moral law, as a law of autonomy, is “the fundamental law of a supersensible nature and of a pure world of the understanding, the counterpart of which is to exist in the sensible world but without infringing upon its laws” (38/5:43). See also Pure Reason, A808/B836.

11 Translators and commentators have offered a number of suggestions for the content of the missing first proposition. Among the more plausible examples of these suggestions is Beck’s: “The first proposition of morality is that to have genuine moral worth, an action must be done from duty.” See Kant, Immanuel, Foundations of the Metaphysics of Morals, 2d ed., trans. Beck, Lewis White (New York: Macmillan, 1990), 15-16Google Scholar.

12 Several have attempted to reconstruct this argument from the context of ideas floating about in the first section of the Groundwork. See, for example, Schönecker, Dieter, “What is the ‘First Proposition’ Regarding Duty in Kant’s Grundlegung?” in Gerhardt, Volker, Horstmann, Rolf-Peter and Schumacher, Ralph, eds., Akten des IX. Internationalen Kant-Kongress, Bd. III: Secktionen VI-X (Berlin: Walter de Gruyter, 2001), 89-95Google Scholar.

13 Gregor’s translation of the main portion of Kant’s sentence here is: “For, all these effects (agreeableness of one’s condition, indeed even promotion of others’ happiness) could have been also brought about by other causes, so that there would have been no need, for this, of the will of a rational being. …”

14 Guyer, Paul, Kant (London: Routledge, 2006), 183Google Scholar.

15 Aune, Bruce, Kant’s Theory of Morals (Princeton, NJ: Princeton University Press, 1979), 28-34Google Scholar. A version of this same criticism has been offered by Wood. He writes that what I am calling step IV in Kant’s argument “tells us no more than that our maxims ought to conform to whatever universal laws there are. It does not tell us how to discover these laws, and it does not entail that maxims conform to the laws whenever they pass the [test] provided for in [the formula of universal law].” See Wood, Allen W., Kant’s Ethical Thought (Cambridge: Cambridge University Press, 1999), 81CrossRefGoogle Scholar; see also 48, 78-9.

16 It is an unargued assumption for Kant that either reason or sensibility—natural instinct, desire or inclination—can determine human beings to action, there being no third possibility. So assuming that motivation to obey divine commands is not of sensible, natural origin, there is no alternative but to say that it is rational. If Kerstein has in mind some third alternative, besides reason and sensibility, he must show on independent grounds that Kant was wrong to assume motivation can be only either rational or sense-based.

17 See Guyer, Kant, 185-6; and “The Derivation of the Categorical Imperative,” 72-3.

18 See Hume, David, An Enquiry concerning the Principles of Morals, ed. Beauchamp, Tom L. (Oxford: Clarendon Press, 1998), 5.45, 6.4, and 6.5Google Scholar.

19 The word translated “as such” is überhaupt; and here, at least, it follows immediately after “actions” (Handlungen). But in several other places, where the same point is made, Kant has überhaupt following “conformity to law” (Gesetzmäßigkeit).

20 See Kant, Immanuel, Groundwork of the Metaphysics of Morals, trans. Paton, H. J. (New York: Harper & Row, 1956), 70/4:402Google Scholar. See also Foundations (trans. Beck), 18; and see Gregor’s translation of some parallel passages, including the sentence quoted in the following note, and at Groundwork, 31/4:421.

21 This conjecture finds support in the sentence Kant wrote following step V of his derivation: “Here mere conformity to universal law as such, without having as its basis some law determined for certain actions, is what serves the will as its principle. …” (15/4:402, emphasis added).

22 Kant, Immanuel, Prolegomena to Any Future Metaphysics that Will Be Able to Come Forward as a Science,Google Scholar trans. Gary Hatfield, in Kant, Immanuel, Theoretical Philosophy after 1781, ed. Allison, Henry and Heath, Peter (Cambridge: Cambridge University Press, 2002), 90-91/4:296Google Scholar.

23 Kant himself draws this analogy in Groundwork II—“Since the universality of law in accordance with which effects take place constitutes what is properly called nature in the most general sense (as regards its form) – that is, the existence of things insofar as it is determined in accordance with universal laws – the universal imperative of duty can also go as follows: act as if the maxim of your action were to become by your will a universal law of nature” (31/4:421). See also Practical Reason, 56/5:65.

24 Later, in the second Critique, in the section on “The Typic of Pure Practical Judgment,” Kant will argue that we are entitled to use the systematic unity of nature as something like a “schema” for moral judgment. This is supposed to parallel the way that we use schemata of the transcendental imagination in applying the categories of understanding in empirical judgment. See Practical Reason, 58-62/5:67-71.

25 See Korsgaard, Creating the Kingdom of Ends, 143.

26 But bear in mind also that the agent restricting freedom, and the agent whose freedom is restricted, might be the same. That is, by acting at one time an agent might unduly restrict his or her freedom to act at another time. Suicide would be the limiting case here. Less drastic examples of this type of self-restriction would be recreational use of addictive drugs, and indentured servitude.