The Critique of Practical Reason | Page 3

also I can understand why the most considerable objections
which I have as yet met with against the Critique turn about these two
points, namely, on the one side, the objective reality of the categories
as applied to noumena, which is in the theoretical department of
knowledge denied, in the practical affirmed; and on the other side, the
paradoxical demand to regard oneself qua subject of freedom as a
noumenon, and at the same time from the point of view of physical
nature as a phenomenon in one's own empirical consciousness; for as
long as one has formed no definite notions of morality and freedom,
one could not conjecture on the one side what was intended to be the
noumenon, the basis of the alleged phenomenon, and on the other side
it seemed doubtful whether it was at all possible to form any notion of
it, seeing that we had previously assigned all the notions of the pure
understanding in its theoretical use exclusively to phenomena. Nothing
but a detailed criticism of the practical reason can remove all this
misapprehension and set in a clear light the consistency which
constitutes its greatest merit.
So much by way of justification of the proceeding by which, in this
work, the notions and principles of pure speculative reason which have
already undergone their special critical examination are, now and then,
again subjected to examination. This would not in other cases be in
accordance with the systematic process by which a science is
established, since matters which have been decided ought only to be
cited and not again discussed. In this case, however, it was not only
allowable but necessary, because reason is here considered in transition
to a different use of these concepts from what it had made of them
before. Such a transition necessitates a comparison of the old and the
new usage, in order to distinguish well the new path from the old one

and, at the same time, to allow their connection to be observed.
Accordingly considerations of this kind, including those which are once
more directed to the concept of freedom in the practical use of the pure
reason, must not be regarded as an interpolation serving only to fill up
the gaps in the critical system of speculative reason (for this is for its
own purpose complete), or like the props and buttresses which in a
hastily constructed building are often added afterwards; but as true
members which make the connexion of the system plain, and show us
concepts, here presented as real, which there could only be presented
problematically. This remark applies especially to the concept of
freedom, respecting which one cannot but observe with surprise that so
many boast of being able to understand it quite well and to explain its
possibility, while they regard it only psychologically, whereas if they
had studied it in a transcendental point of view, they must have
recognized that it is not only indispensable as a problematical concept,
in the complete use of speculative reason, but also quite
incomprehensible; and if they afterwards came to consider its practical
use, they must needs have come to the very mode of determining the
principles of this, to which they are now so loth to assent. The concept
of freedom is the stone of stumbling for all empiricists, but at the same
time the key to the loftiest practical principles for critical moralists,
who perceive by its means that they must necessarily proceed by a
rational method. For this reason I beg the reader not to pass lightly over
what is said of this concept at the end of the Analytic.
I must leave it to those who are acquainted with works of this kind to
judge whether such a system as that of the practical reason, which is
here developed from the critical examination of it, has cost much or
little trouble, especially in seeking not to miss the true point of view
from which the whole can be rightly sketched. It presupposes, indeed,
the Fundamental Principles of the Metaphysic of Morals, but only in so
far as this gives a preliminary acquaintance with the principle of duty,
and assigns and justifies a definite formula thereof; in other respects it
is independent. * It results from the nature of this practical faculty itself
that the complete classification of all practical sciences cannot be added,
as in the critique of the speculative reason. For it is not possible to
define duties specially, as human duties, with a view to their

classification, until the subject of this definition (viz., man) is known
according to his actual nature, at least so far as is necessary with
respect to duty; this, however, does not belong to a critical examination
of the practical reason, the business of which is