synthetical proposition. It is synthetical because by analysis of the concept of an
absolutely good will that property of the maxim cannot be found in it. Such synthetical
propositions, however, are made possible only by the fact that the two cognitions are
connected with each other through their union with a third in which both are to be found.
The positive concept of freedom furnishes this third cognition, which cannot be, as in the
case of physical causes, the sensible world of nature, in the concept of which we find
conjoined the concepts of something as cause in relation to something else as effect. We
cannot yet show directly what this third cognition is to which freedom directs us and of
which we have an a prioriIdea, nor can we yet explain the deduction of the concept of
freedom from pure practical reason, and therewith the possibility of a categorical imper-
ative. For this, some further preparation is needed.
Freedom Must be Presupposed as the Property of the Will of All Rational BeingsIt is not enough to ascribe freedom to our will, on whatever grounds, if we do not
also have sufficient grounds for attributing it to all rational beings. For since morality
serves as a law for us only as rational beings, it must hold for all rational beings, and
since it must be derived exclusively from the property of freedom, freedom as a property
of the will of all rational beings must be demonstrated. And it does not suffice to prove it
from certain alleged experiences of human nature (which is indeed impossible, as it can
be proved only a priori), but we must prove it as belonging universally to the activity of
rational beings endowed with a will. Now I say that every being which cannot act other-
wise than under the Idea of freedom is thereby really free in a practical respect. That is to
say, all laws which are inseparably bound with freedom hold for it just as if its wills were
proved free in itself by theoretical philosophy.* Now I affirm that we must necessarily
grant that every rational being who has a will also has the Idea of freedom and that it acts
only under this Idea. For in such a being we think of a reason which is practical (i.e., a
reason which has causality with respect to its object). Now we cannot conceive of a
reason which, in making its judgments, consciously responds to a bidding from the
outside, for then the subject would attribute the determination of its power of judgment
not to reason but to an impulse. Reason must regard itself as the author of its principles,
independently of alien influences; consequently as practical reason or as the will of a
rational being it must regard itself as free. That is to say, the will of a rational being can
be a will of its own only under the Idea of freedom, and therefore from a practical point
of view such a will must be ascribed to all rational beings.
Of the Interest Attaching to the Ideas of MoralityWe have finally reduced the definite concept of morality to the Idea of freedom,
but we could not prove freedom to be actual in ourselves and in human nature. We saw
only that we must presuppose it if we would think of a being as rational and conscious
of its causality with respect to actions, that is, as endowed with a will; and so we find
that on the very same grounds we must ascribe to each being endowed with reason and
will the property of determining itself to action under the Idea of its freedom.
FOUNDATIONS OF THEMETAPHYSICS OFMORALS 885
448449*I propose this argument as sufficient to our purpose: Freedom as an Idea is posited by all rational
beings as the basis for their actions. I do so in order to avoid having to prove freedom also in its theoretical
aspect. For even if the latter is left unproved, the laws which would obligate a being who was really free
would hold for a being who cannot act except under the Idea of his own freedom. Thus we escape the onus
which has been pressed on theory.