The Principles of Pure Practical Reason (Preface, Introduction, Analytic, Chapter I)

Preface

This work is called a Critique of Practical Reason, not of pure practical reason. For it is only to show that there is pure practical reason, and for this purpose it criticises reason's entire practical faculty. If it succeeds in this, it needs no critique of the pure faculty itself, to see whether reason oversteps itself in such a claim, as happens with speculative reason. For if, as pure reason, it is really practical, it proves its reality and that of its concepts by what it does, and all reasoning against the possibility of its being so is futile.

With this faculty, transcendental freedom is also established. The concept of freedom, insofar as its reality is proved by an apodictic law of practical reason, constitutes the keystone of the whole structure of a system of pure reason, even of speculative reason. All other concepts — those of God and immortality — which, as mere ideas, remain without support in speculative reason, now attach themselves to it, and with it and through it acquire stability and objective reality.

Freedom is the condition of the moral law; but the moral law is the condition under which we can first become aware of freedom. Freedom is the ratio essendi of the moral law, but the moral law is the ratio cognoscendi of freedom. For had not the moral law already been distinctly thought in our reason, we should never consider ourselves entitled to assume such a thing as freedom, although it is not self-contradictory. But were there no freedom, the moral law would not be found in us at all.

"Ratio essendi": the reason why something is; "ratio cognoscendi": the reason why we know it. Freedom is why there is a moral law; the moral law is how we know there is freedom.

Introduction

The theoretical use of reason was concerned with objects of the cognitive faculty alone. The practical use of reason is concerned with the determining grounds of the will — a faculty either of producing objects corresponding to representations, or of determining itself to effect such objects, that is, of determining its causality. The question is whether pure reason by itself suffices to determine the will, or whether it can be a determining ground of the will only as empirically conditioned.

Chapter I: The Principles of Pure Practical Reason

Practical principles are propositions that contain a general determination of the will. They are subjective, or maxims, when the condition is regarded by the subject as valid only for his own will; but they are objective, or practical laws, when the condition is cognised as objective, that is, valid for the will of every rational being.

Imperatives are either hypothetical — "If you want this, do that" — or categorical: they command unconditionally, without regard to any end we may have.

The "categorical imperative" was first set out in the "Groundwork" (1785).

All material practical principles — those that presuppose an object of desire as the determining ground of the will — are, without exception, of one and the same kind, and belong under the general principle of self-love, or one's own happiness. To be happy is necessarily the demand of every rational but finite being; but because it depends on what pleases this or that person, it can never furnish a law. Here, one man's taste is not another's.

Kant remarks ironically that if universal happiness were taken as law, there would be a harmony like that described in a satirical poem about a married couple bent on ruining each other: "O marvellous harmony! What he wants, she wants too"; or like King Francis I's pledge to the Emperor Charles V: "What my brother Charles wants, I want too" — namely, Milan.

If a rational being is to think of his maxims as practical universal laws, he can think of them only as principles that contain the determining ground of the will not by their matter but merely by their form.

So we arrive at the fundamental law of pure practical reason:

So act that the maxim of your will could always hold at the same time as a principle in a giving of universal law.

This is Kant's formula of the categorical imperative in this book. The "Groundwork" gives it as: "Act only according to that maxim through which you can at the same time will that it become a universal law."

The consciousness of this fundamental law may be called a fact of reason, because one cannot reason it out from antecedent data of reason — for example, from the consciousness of freedom, since this is not antecedently given to us — but because it forces itself upon us of itself as a synthetic a priori proposition that is not based on any intuition.

The "fact of reason" (Faktum der Vernunft) is one of the most discussed ideas in the book: the moral law is not proved, but simply found, as a given of rational consciousness.

Kant gives an example. Suppose someone asserts of his lustful inclination that, when the desired object and the opportunity are present, it is quite irresistible to him. Ask him whether, if a gallows were erected in front of the house where he finds this opportunity, and he would be hanged on it immediately after gratifying his lust, he would not then control his inclination. One need not conjecture very long what he would reply. But ask him whether, if his prince demanded, on pain of the same immediate execution, that he give false testimony against an honourable man whom the prince wished to destroy under a plausible pretext, he would consider it possible to overcome his love of life, however great it may be. He would perhaps not venture to assert whether he would do it or not; but he must admit without hesitation that it would be possible for him. He judges, therefore, that he can do something because he is aware that he ought to do it, and he cognises freedom within him, which, without the moral law, would have remained unknown to him.

The example shows how the moral law reveals freedom: we know we could refuse, because we know we ought to.

Pure reason is practical of itself alone, and gives to man a universal law, which we call the moral law.

The autonomy of the will is the sole principle of all moral laws and of the duties in keeping with them. Heteronomy of choice, on the other hand, not only does not ground any obligation at all, but is opposed to its principle and to the morality of the will.

Autonomy: the will gives itself its own law. Heteronomy: the will is determined by something outside it — desire, pleasure, fear, or the command of another.

How easily the commonest understanding can tell what form of maxim is suitable for universal law! Suppose I have made it my maxim to increase my wealth by every safe means. Now I have in my hands a deposit, whose owner has died and left no record of it. Naturally this is a case for my maxim. Now I only want to know whether this maxim could also hold as a universal practical law. I apply it to the case and ask whether it could take the form of a law: "Everyone may deny a deposit which no one can prove has been made." I at once become aware that such a principle, as a law, would annihilate itself, because it would bring it about that there would be no deposits at all.

Kant then reviews all the "material" principles of morality ever proposed — subjective ones, such as education (Montaigne), the civil constitution (Mandeville), physical feeling (Epicurus), moral feeling (Hutcheson); and objective ones, such as perfection (Wolff and the Stoics) and the will of God (Crusius and other theological moralists) — and shows that all are heteronomous, and none can furnish a universal law.