be answered to this extent, that we can assign the only hypothesis
on which it is possible, namely, the idea of freedom; and we can
also discern the necessity of this hypothesis, and this is
sufficient for the practical exercise of reason, that is, for the
conviction of the validity of this imperative, and hence of the
moral law; but how this hypothesis itself is possible can never be
discerned by any human reason. On the hypothesis, however, that the
will of an intelligence is free, its autonomy, as the essential formal
condition of its determination, is a necessary consequence.
Moreover, this freedom of will is not merely quite possible as a
hypothesis (not involving any contradiction to the principle of
physical necessity in the connexion of the phenomena of the sensible
world) as speculative philosophy can show: but further, a rational
being who is conscious of causality through reason, that is to say, of
a will (distinct from desires), must of necessity make it practically,
that is, in idea, the condition of all his voluntary actions. But to
explain how pure reason can be of itself practical without the aid
of any spring of action that could be derived from any other source,
i.e., how the mere principle of the universal validity of all its
maxims as laws (which would certainly be the form of a pure
practical reason) can of itself supply a spring, without any matter
(object) of the will in which one could antecedently take any
interest; and how it can produce an interest which would be called
purely moral; or in other words, how pure reason can be practical-
to explain this is beyond the power of human reason, and all the
labour and pains of seeking an explanation of it are lost.
It is just the same as if I sought to find out how freedom itself is
possible as the causality of a will. For then I quit the ground of
philosophical explanation, and I have no other to go upon. I might
indeed revel in the world of intelligences which still remains to
me, but although I have an idea of it which is well founded, yet I
have not the least knowledge of it, nor an I ever attain to such
knowledge with all the efforts of my natural faculty of reason. It
signifies only a something that remains over when I have eliminated
everything belonging to the world of sense from the actuating
principles of my will, serving merely to keep in bounds the
principle of motives taken from the field of sensibility; fixing its
limits and showing that it does not contain all in all within
itself, but that there is more beyond it; but this something more I
know no further. Of pure reason which frames this ideal, there remains
after the abstraction of all matter, i.e., knowledge of objects,
nothing but the form, namely, the practical law of the universality of
the maxims, and in conformity with this conception of reason in
reference to a pure world of understanding as a possible efficient
cause, that is a cause determining the will. There must here be a
total absence of springs; unless this idea of an intelligible world is
itself the spring, or that in which reason primarily takes an
interest; but to make this intelligible is precisely the problem
that we cannot solve.
Here now is the extreme limit of all moral inquiry, and it is of
great importance to determine it even on this account, in order that
reason may not on the one hand, to the prejudice of morals, seek about
in the world of sense for the supreme motive and an interest
comprehensible but empirical; and on the other hand, that it may not
impotently flap its wings without being able to move in the (for it)
empty space of transcendent concepts which we call the intelligible
world, and so lose itself amidst chimeras. For the rest, the idea of a
pure world of understanding as a system of all intelligences, and to
which we ourselves as rational beings belong (although we are likewise
on the other side members of the sensible world), this remains
always a useful and legitimate idea for the purposes of rational
belief, although all knowledge stops at its threshold, useful, namely,
to produce in us a lively interest in the moral law by means of the
noble ideal of a universal kingdom of ends in themselves (rational
beings), to which we can belong as members then only when we carefully
conduct ourselves according to the maxims of freedom as if they were
laws of nature.
Concluding Remark
The speculative employment of reason with respect to nature leads to
the absolute necessity of some supreme cause of the world: the
practical employment of reason with a view to freedom leads also to
absolute necessity, but only of the laws of the actions of a
rational being as such. Now it is an essential principle of reason,
however employed, to push its knowledge to a consciousness of its
necessity (without which it would not be rational knowledge). It is,
however, an equally essential restriction of the same reason that it
can neither discern the necessity of what is or what happens, nor of
what ought to happen, unless a condition is supposed on which it is or
happens or ought to happen. In this way, however, by the constant
inquiry for the condition, the satisfaction of reason is only
further and further postponed. Hence it unceasingly seeks the
unconditionally necessary and finds itself forced to assume it,
although without any means of making it comprehensible to itself,
happy enough if only it can discover a conception which agrees with
this assumption. It is therefore no fault in our deduction of the
supreme principle of morality, but an objection that should be made to
human reason in general, that it cannot enable us to conceive the
absolute necessity of an unconditional practical law (such as the
categorical imperative must be). It cannot be blamed for refusing to
explain this necessity by a condition, that is to say, by means of
some interest assumed as a basis, since the law would then cease to be
a supreme law of reason. And thus while we do not comprehend the
practical unconditional necessity of the moral imperative, we yet
comprehend its incomprehensibility, and this is all that can be fairly
demanded of a philosophy which strives to carry its principles up to
the very limit of human reason.
THE END