principles-a theoretical, as philosophy of nature, and a practical, as
philosophy of morals (for this is what the practical legislation of
reason by the concept of freedom is called). Hitherto, however, in the
application of these expressions to the division of the different
principles, and with them to the division of philosophy, a gross
misuse of the terms has prevailed; for what is practical according
to concepts of nature bas been taken as identical with what is
practical according to the concept of freedom, with the result that
a division has been made under these heads of theoretical and
practical, by which, in effect, there has been no division at all
(seeing that both parts might have similar principles).

  The will-for this is what is said-is the faculty of desire and, as
such, is just one of the many natural causes in the world, the one,
namely, which acts by concepts; and whatever is represented as
possible (or necessary) through the efficacy of will is called
practically possible (or necessary): the intention being to
distinguish its possibility (or necessity) from the physical
possibility or necessity of an effect the causality of whose cause
is not determined to its production by concepts (but rather, as with
lifeless matter, by mechanism, and, as with the lower animals, by
instinct). Now, the question in respect of the practical faculty:
whether, that is to say, the concept, by which the causality of the
will gets its rule, is a concept of nature or of freedom, is here left
quite open.

  The latter distinction, however, is essential. For, let the
concept determining the causality be a concept of nature, and then the
principles are technically-practical; but, let it be a concept of
freedom, and they are morally-practical. Now, in the division of a
rational science the difference between objects that require different
principles for their cognition is the difference on which everything
turns. Hence technically-practical principles belong to theoretical
philosophy (natural science), whereas those morally-practical alone
form the second part, that is, practical philosophy (ethical science).

  All technically-practical rules (i.e., those of art and skill
generally, or even of prudence, as a skill in exercising an
influence over men and their wills) must, so far as their principles
rest upon concepts, be reckoned only as corollaries to theoretical
philosophy. For they only touch the possibility of things according to
concepts of nature, and this embraces, not alone the means
discoverable in nature for the purpose, but even the will itself (as a
faculty of desire, and consequently a natural faculty), so far as it
is determinable on these rules by natural motives. Still these
practical rules are not called laws (like physical laws), but only
precepts. This is due to the fact that the will does not stand
simply under the natural concept, but also under the concept of
freedom. In the latter connection its principles are called laws,
and these principles, with the addition of what follows them, alone
constitute the second at practical part of philosophy.

  The solution of the problems of pure geometry is not allocated to
a special part of that science, nor does the art of land-surveying
merit the name of practical, in contradistinction to pure, as a second
part of the general science of geometry, and with equally little, or
perhaps less, right can the mechanical or chemical art of experiment
or of observation be ranked as a practical part of the science of
nature, or, in fine, domestic, agricultural, or political economy, the
art of social intercourse, the principles of dietetics, or even
general instruction as to the attainment of happiness, or as much as
the control of the inclinations or the restraining of the affections
with a view thereto, be denominated practical philosophy-not to
mention forming these latter in a second part of philosophy in
general. For, between them all, the above contain nothing more than
rules of skill, which are thus only technically practical-the skill
being directed to producing an effect which is possible according to
natural concepts of causes and effects. As these concepts belong to
theoretical philosophy, they are subject to those precepts as mere
corollaries of theoretical philosophy (i.e., as corollaries of natural
science), and so cannot claim any place in any special philosophy
called practical. On the other hand, the morally practical precepts,
which are founded entirely on the concept of freedom, to the
complete exclusion of grounds taken from nature for the
determination of the will, form quite a special kind of precepts.
These, too, like the rules obeyed by nature, are, without
qualification, called laws-though they do not, like the latter, rest
on sensible conditions, but upon a supersensible principle-and they
must needs have a separate part of philosophy allotted to them as
their own, corresponding to the theoretical part, and termed practical
philosophy capable

  Hence it is evident that a complex of practical precepts furnished
by philosophy does not form a special part of philosophy,
co-ordinate with the theoretical, by reason of its precepts being
practical-for that they might be, notwithstanding that their
principles were derived wholly from the theoretical knowledge of
nature (as technically-practical rules). But an adequate reason only
exists where their principle, being in no way borrowed from the
concept of nature, which is always sensibly conditioned, rests
consequently on the supersensible, which the concept of freedom
alone makes cognizable by means of its formal laws, and where,
therefore, they are morally-practical, i. e., not merely precepts
and its and rules in this or that interest, but laws independent of
all antecedent reference to ends or aims.

            II. The Realm of Philosophy in General.

  The employment of our faculty of cognition from principles, and with
it philosophy, is coextensive with the applicability of a priori