Philosophic Classics From Plato to Derrida

How such a synthetical practical a prioriproposition is possible and why it is

necessary is a problem whose solution does not lie within the boundaries of the

metaphysics of morals. Moreover, we have not here affirmed its truth, and even less

professed to command a proof of it. We showed only through the development of the

generally received concept of morals that autonomy of the will is unavoidably con-

nected with it, or rather that it is its foundation. Whoever, therefore, holds morality

to be something real and not a chimerical idea without truth must also concede its

principle which has been derived here. Consequently, this section, like the first, was

merely analytical. To prove that morality is not a mere phantom of the mind—and if

the categorical imperative, and with it the autonomy of the will, is true and

absolutely necessary as an a prioriproposition, it follows that it is no phantom—

requires that a synthetical use of pure practical reason be possible. But we must not

venture on this use without first making a critical examination of this faculty of

reason. In the last section we shall give the principal features of such an examination

that will be sufficient for our purpose.

THIRDSECTION

TRANSITION FROM THEMETAPHYSICS OFMORALS TO THECRITICAL

EXAMINATION OFPUREPRACTICALREASON

The Concept of Freedom Is the Key to the Explanation of the Autonomy of the Will

As will is a kind of causality of living beings so far as they are rational, freedom

would be that property of this causality by which it can be effective independent of

foreign causes determining it, just as natural necessity is the property of the causality

of all irrational beings by which they are determined to activity by the influence of

foreign causes.

The preceding definition of freedom is negative and therefore affords no insight

into its essence. But a positive concept of freedom flows from it which is so much the

richer and more fruitful. Since the concept of a causality entails that of laws according

to which something (i.e., the effect) must be established through something else which

we call cause, it follows that freedom is by no means lawless even though it is not a

property of the will according to laws of nature. Rather, it must be a causality of a pecu-

liar kind according to immutable laws. Otherwise a free will would be an absurdity.

Natural necessity is, as we have seen, a heteronomy of efficient causes, for every effect

is possible only according to the law that something else determines the efficient cause

to its causality. What else, then, can the freedom of the will be but autonomy (i.e., the

property of the will to be law to itself)? The proposition that the will is a law to itself in

all its actions, however, only expresses the principle that we should act according to no

other maxim than that which can also have itself as a universal law for its object. And

this is just the formula of the categorical imperative and the principle of morality.

Therefore a free will and a will under moral laws are identical.

Thus if freedom of the will is presupposed, morality together with its principle fol-

lows from it by the mere analysis of its concepts. But the principle: An absolutely good

will is one whose maxim can always include itself as a universal law, is nevertheless a

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