The Kantian Ethics: Metaphysics of Morals, The Critique of Practical Reason & Perpetual Peace. Immanuel Kant
Third Section
Transition from the Metaphysic of Morals to the Critique of Pure Practical Reason
The Concept of Freedom is the Key that explains the Autonomy of the Will
The will is a kind of causality belonging to living beings in so far as they are rational, and freedom would be this property of such causality that it can be efficient, independently of foreign causes determining it; just as physical necessity is the property that the causality of all irrational beings has of being determined to activity by the influence of foreign causes.
The preceding definition of freedom is negative and therefore unfruitful for the discovery of its essence, but it leads to a positive conception which is so much the more full and fruitful.
Since the conception of causality involves that of laws, according to which, by something that we call cause, something else, namely the effect, must be produced; hence, although freedom is not a property of the will depending on physical laws, yet it is not for that reason lawless; on the contrary it must be a causality acting according to immutable laws, but of a peculiar kind; otherwise a free will would be an absurdity. Physical necessity is a heteronomy of the efficient causes, for every effect is possible only according to this law, that something else determines the efficient cause to exert its causality. What else then can freedom of the will be but autonomy, that is, the property of the will to be a law to itself? But the proposition: "The will is in every action a law to itself," only expresses the principle: "To act on no other maxim than that which can also have as an object itself as a universal law." Now this is precisely the formula of the categorical imperative and is the principle of morality, so that a free will and a will subject to moral laws are one and the same.
On the hypothesis, then, of freedom of the will, morality together with its principle follows from it by mere analysis of the conception. However, the latter is a synthetic proposition; viz., an absolutely good will is that whose maxim can always include itself regarded as a universal law; for this property of its maxim can never be discovered by analysing the conception of an absolutely good will. Now such synthetic propositions are only possible in this way: that the two cognitions are connected together by their union with a third in which they are both to be found. The positive concept of freedom furnishes this third cognition, which cannot, as with physical causes, be the nature of the sensible world (in the concept of which we find conjoined the concept of something in relation as cause to something else as effect). We cannot now at once show what this third is to which freedom points us and of which we have an idea a priori, nor can we make intelligible how the concept of freedom is shown to be legitimate from principles of pure practical reason and with it the possibility of a categorical imperative; but some further preparation is required.
Freedom must be presupposed as a Property of the Will of all Rational Beings
It is not enough to predicate freedom of our own will, from whatever reason, if we have not sufficient grounds for predicating the same of all rational beings. For as morality serves as a law for us only because we are rational beings, it must also hold for all rational beings; and as it must be deduced simply from the property of freedom, it must be shown that freedom also is a property of all rational beings. It is not enough, then, to prove it from certain supposed experiences of human nature (which indeed is quite impossible, and it can only be shown a priori), but we must show that it belongs to the activity of all rational beings endowed with a will. Now I say every being that cannot act except under the idea of freedom is just for that reason in a practical point of view really free, that is to say, all laws which are inseparably connected with freedom have the same force for him as if his will had been shown to be free in itself by a proof theoretically conclusive.17 Now I affirm that we must attribute to every rational being which has a will that it has also the idea of freedom and acts entirely under this idea. For in such a being we conceive a reason that is practical, that is, has causality in reference to its objects. Now we cannot possibly conceive a reason consciously receiving a bias from any other quarter with respect to its judgements, for then the subject would ascribe the determination of its judgement not to its own reason, but to an impulse. It must regard itself as the author of its principles independent of foreign 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 such a being cannot be a will of its own except under the idea of freedom. This idea must therefore in a practical point of view be ascribed to every rational being.
Of the Interest attaching to the Ideas of Morality
We have finally reduced the definite conception of morality to the idea of freedom. This latter, however, we could not prove to be actually a property of ourselves or of human nature; only we saw that it must be presupposed if we would conceive a being as rational and conscious of its causality in respect of its actions, i.e., as endowed with a will; and so we find that on just the same grounds we must ascribe to every being endowed with reason and will this attribute of determining itself to action under the idea of its freedom.
Now it resulted also from the presupposition of these ideas that we became aware of a law that the subjective principles of action, i.e., maxims, must always be so assumed that they can also hold as objective, that is, universal principles, and so serve as universal laws of our own dictation. But why then should I subject myself to this principle and that simply as a rational being, thus also subjecting to it all other being endowed with reason? I will allow that no interest urges me to this, for that would not give a categorical imperative, but I must take an interest in it and discern how this comes to pass; for this properly an "I ought" is properly an "I would," valid for every rational being, provided only that reason determined his actions without any hindrance. But for beings that are in addition affected as we are by springs of a different kind, namely, sensibility, and in whose case that is not always done which reason alone would do, for these that necessity is expressed only as an "ought," and the subjective necessity is different from the objective.
It seems then as if the moral law, that is, the principle of autonomy of the will, were properly speaking only presupposed in the idea of freedom, and as if we could not prove its reality and objective necessity independently. In that case we should still have gained something considerable by at least determining the true principle more exactly than had previously been done; but as regards its validity and the practical necessity of subjecting oneself to it, we should not have advanced a step. For if we were asked why the universal validity of our maxim as a law must be the condition restricting our actions, and on what we ground the worth which we assign to this manner of acting — a worth so great that there cannot be any higher interest; and if we were asked further how it happens that it is by this alone a man believes he feels his own personal worth, in comparison with which that of an agreeable or disagreeable condition is to be regarded as nothing, to these questions we could give no satisfactory answer.
We find indeed sometimes that we can take an interest in a personal quality which does not involve any interest of external condition, provided this quality makes us capable of participating in the condition in case reason were to effect the allotment; that is to say, the mere being worthy of happiness can interest of itself even without the motive of participating in this happiness. This judgement, however, is in fact only the effect of the importance of the moral law which we before presupposed (when by the idea of freedom we detach ourselves from every empirical interest); but that we ought to detach ourselves from these interests, i.e., to consider ourselves as free in action and yet as subject to certain laws, so as to find a worth simply in our own person which can compensate us for the loss of everything that gives worth to our condition; this we are not yet able to discern in this way, nor do we see how it is possible so to act — in other words, whence the moral law derives its obligation.
It must be freely admitted that there is a sort of circle here