286 Kant: A Biographyof ordinary moral agents. He deals, rather, with an ideal of pure reason that
is entirely a priori.^42 This ideal, which he calls the categorical imperative, is
not "given in experience." It is "an a priori synthetic practical proposition,"
whose very possibility is difficult to "see."^43 Indeed, Kant ends his book by
emphasizing that "we do not... comprehend the practical unconditional
necessity of the moral imperative." We only "comprehend its incompre¬
hensibility," and this "is all that can fairly be required of a philosophy that
strives in its principles to the very boundary of human reason."^44
So morality for Kant is an enigma. The ultimate condition of the pos¬
sibility of morality cannot be understood. One might be tempted to say
that it is a brute fact, even if it is the brute fact that one is rational and thus
has the "idea of another and far worthier purpose of one's existence." That
the "mere dignity of humanity as rational nature, without any other end or
advantage to be attained by it — hence respect for a mere idea - is yet to serve
as an inflexible precept of the will" is, Kant openly acknowledges, a para¬
dox. True morality is an ideal yet to be instantiated in the world, but it is
the only ideal worth striving for. This is in the end what his idealism amounts
to. Kant knew, moreover, that this notion of the "dignity of humanity"
would have explosive consequences if adopted by the citizens of Prussia
and the rest of Europe, even if he himself was careful to downplay the rev¬
olutionary implications of his work.
Kant formulates the categorical imperative, that is, the unconditional
command of morality, in three different ways, all of which are supposed
to be equivalent. In its first formulation it reads: "«cf only in accordance
with that maxim through which you can at the same time will that it become a
universal lam"** The second formulation says: "So act that you use human¬
ity, whether in your own person or in the person of any other, always at the same
time as an end, never merely as a means." The third version amounts to the
claim that "every rational being" must be understood "as one who must
regard himself as giving universal law through all the maxims of his will."^46
Kant most clearly identifies it as the "formal principle" of the maxims in
which an agent views himself as a lawgiver in the kingdom of ends, with
the command: "Act as if your maxims were to serve at the same time as a
universal law (for all rational beings)."^47 Though Kant - followed by most
of his commentators — seems to favor the first version of the categorical
imperative, it is really the last one that is most fruitful for Kant's further
argument, for it is what allows him to introduce the idea of a kingdom of
ends as opposed to a kingdom of nature, and to distinguish autonomy from
heteronomy.