The Critique of Practical Reason
Kant, Immanuel, 1724-1804
English
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1788
THE CRITIQUE OF PRACTICAL REASON
by Immanuel Kant
translated by Thomas Kingsmill Abbott
PREFACE.
This work is called the Critique of Practical Reason, not of the
pure practical reason, although its parallelism with the speculative
critique would seem to require the latter term. The reason of this
appears sufficiently from the treatise itself. Its business is to show
that there is pure practical reason, and for this purpose it
criticizes the entire practical faculty of reason. If it succeeds in
this, it has no need to criticize the pure faculty itself in order
to see whether reason in making such a claim does not presumptuously
overstep itself (as is the case with the speculative reason). For
if, as pure reason, it is actually practical, it proves its own
reality and that of its concepts by fact, and all disputation
against the possibility of its being real is futile.
With this faculty, transcendental freedom is also established;
freedom, namely, in that absolute sense in which speculative reason
required it in its use of the concept of causality in order to
escape the antinomy into which it inevitably falls, when in the
chain of cause and effect it tries to think the unconditioned.
Speculative reason could only exhibit this concept (of freedom)
problematically as not impossible to thought, without assuring it
any objective reality, and merely lest the supposed impossibility of
what it must at least allow to be thinkable should endanger its very
being and plunge it into an abyss of scepticism.
Inasmuch as the reality of the concept of freedom is proved by an
apodeictic law of practical reason, it is the keystone of the whole
system of pure reason, even the speculative, and all other concepts
(those of God and immortality) which, as being mere ideas, remain in
it unsupported, now attach themselves to this concept, and by it
obtain consistence and objective reality; that is to say, their
possibility is proved by the fact that freedom actually exists, for
this idea is revealed by the moral law.
Freedom, however, is the only one of all the ideas of the
speculative reason of which we know the possibility a priori (without,
however, understanding it), because it is the condition of the moral
law which we know. * The ideas of God and immortality, however, are
not conditions of the moral law, but only conditions of the necessary
object of a will determined by this law; that is to say, conditions of
the practical use of our pure reason. Hence, with respect to these
ideas, we cannot affirm that we know and understand, I will not say
the actuality, but even the possibility of them. However they are
the conditions of the application of the morally determined will to
its object, which is given to it a priori, viz., the summum bonum.
Consequently in this practical point of view their possibility must be
assumed, although we cannot theoretically know and understand it. To
justify this assumption it is sufficient, in a practical point of
view, that they contain no intrinsic impossibility (contradiction).
Here we have what, as far as speculative reason is concerned, is a
merely subjective principle of assent, which, however, is
objectively valid for a reason equally pure but practical, and this
principle, by means of the concept of freedom, assures objective
reality and authority to the ideas of God and immortality. Nay,
there is a subjective necessity (a need of pure reason) to assume
them. Nevertheless the theoretical knowledge of reason is not hereby
enlarged, but only the possibility is given, which heretofore was
merely a problem and now becomes assertion, and thus the practical use
of reason is connected with the elements of theoretical reason. And
this need is not a merely hypothetical one for the arbitrary
purposes of speculation, that we must assume something if we wish in
speculation to carry reason to its utmost limits, but it is a need
which has the force of law to assume something without which that
cannot be which we must inevitably set before us as the aim of our
action.
{PREFACE ^paragraph 5}
* Lest any one should imagine that he finds an inconsistency here
when I call freedom the condition of the moral law, and hereafter
maintain in the treatise itself that the moral law is the condition
under which we can first become conscious of freedom, I will merely
remark that freedom is the ratio essendi of the moral law, while the
moral law is the ratio cognoscendi of freedom. For Pad not the moral
law been previously distinctly thought in our reason, we should
never consider ourselves justified in assuming such a thing as
freedom, although it be not contradictory. But were there no freedom
it would be impossible to trace the moral law in ourselves at all.
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