Ak. 4:424-427 (recommended)
If we now attend to ourselves in every transgression of a duty, we find that we actually do not will that our maxim should become a universal law, since that is impossible for us, but that its opposite should rather generally remain a law; we just take the liberty of making an exception to it for ourselves, orr (just for this once) to the advantage of our inclination. Consequently, if we considered everything from one and the same point of view, namely that of reason, we would find a contradiction in our own will, namely that a certain principle be objectively necessary as a universal law and yet subjectively should not hold universally, but allow of exceptions. But since we consider our action at one time from the point of view of a will that entirely conforms with reason, but then just the same action also from the point of view of a will affected by inclination, there is actually no contradiction here, but rather a resistance of inclination to the prescription of reason (antagonismus), by which the universality of the principle (universalitas) is transformed into a mere general validity (generalitas), and by this the practical rational principle is meant to meet the maxim halfway. Now, even though this cannot be justified in our own impartially employed judgment, it still proves that we actually acknowledge the validity of the categorical imperative, and permit ourselves (with all respect for it) just a few exceptions that, as it seems to us, are immaterial and wrenched from us.
4:425 We have thus established at least this much, that if duty is a concept that is to contain significance and actual legislation for our actions it can be expressed only in categorical imperatives, but by no means in hypothetical ones; likewise we have – and this is already a lot – presented distinctly and determined for every use the content of the categorical imperative, which would have to contain the principle of all duty (if there were such a thing at all). But we are not yet ready to prove a priori that such an imperative is actually in place, that there is a practical law, which commands of itself, absolutely and without any incentives, and that following this law is one’s duty.
For the purpose of achieving this, it is of the utmost importance to let this serve as a warning, that one must put the thought right out of one’s mind that the reality of this principle can be derived from some particular property of human nature. For duty is to be practical unconditional necessity of action; it must thus hold for all rational beings (to which an imperative can at all apply), and only in virtue of this be a law also for every human will. By contrast, whatever is derived from the special natural predisposition of humanity, from certain feelings and propensity, and indeed even, possibly, from a special tendency peculiar to human reason, and would not have to hold necessarily for the will of every rational being – that can indeed yield a maxim for us, but not a law, a subjective principle on which propensity and inclination would fain have us act, but not an objective principle on which we would be instructed to act even if every propensity, inclination and natural arrangement of ours were against it; so much so that it proves the sublimitys and inner dignity of the command in a duty all the more, the less the subjective causes are in favor of it, and the more they are against it, without thereby weakening in the least the necessitation by the law, or taking anything away from its validity.
Here, then, we in fact see Philosophy placed on a precarious standpoint, which is to be firm even though there is nothing either in heaven, or on earth, from which she is suspended, or on which she relies. Here she is to prove her purity, as the sovereign legislatrix15 of her laws, not as the herald of those that an implanted sense, or who knows what tutelary nature whispers to her, which yet – though they may still be better 4:426 than nothing at all – can one and all never make principles that reason dictates, and that must have their source, and with it at the same time their commanding repute, altogether completely a priori: to expect nothing from the inclination of a human being, but everything from the authority of the law and the respect owed to it or, if not, condemn the human being to self-contempt and inner loathing.
Thus everything that is empirical is not only quite unfit to be added to the principle of morality, it is also most disadvantageous to the purity of morals themselves, in which the actual worth of a will absolutely good and elevated above any price consists precisely in this: that the principle of action is free from all influences of contingent grounds, which only experience can furnish. Against this slackness or even base way of thinking, in seeking to identify the principle from among empirical motives and laws, one cannot actually issue too many or too frequent a warning, as human reason in its weariness gladly rests upon this cushion, and in the dream of sweet pretenses (which instead of Juno let it embrace a cloud)16 foists on morality a bastard patched up from limbs of quite varied ancestry, which resembles whatever one wants to see in it, but not Virtue, for him who has once beheld her in her true form.*
The question therefore is this: is it a necessary law for all rational beings always to judge their actions according to maxims of which they themselves can will that they serve as universal laws? If it is, then it must (completely a priori) already be bound up with the concept of the will of a rational being as such. But in order to discover this connection one must, however reluctantly, take a step outside, namely into metaphysics, if into a region of it that differs from that of speculative philosophy, namely into the metaphysics of morals. 4:427 In a practical philosophy, where we are not concerned with accepting grounds of what happens, but rather laws of what ought to happen, even if it never does, i.e. objective practical laws: there we do not need to investigate the grounds of why something pleases or displeases, how the gratification of mere sensation differs from taste, and whether the latter differs from a universal delight of reason; on what feeling pleasure and displeasure rests, and how from this there arise desires and inclinations, and from them, by cooperation of reason, maxims; for all of that belongs to an empirical doctrine of the soul, which would constitute the second part of the doctrine of nature, if considered as philosophy of nature, in so far as it is founded on empirical laws. But here the objective practical law is at issue, and hence the relation of a will to itself, in so far as it determines itself merely through reason, and then everything that has reference to empirical matters is of itself ruled out; because if reason all by itself determines conduct (the possibility of which is just what we now want to investigate), it must necessarily do this a priori.
Ak. 4:427-430 (required)
The will is thought as a capacity to determine itself t to action in conformity with the representation of certain laws. And such a capacity can be found only in rational beings. Now, what serves the will as the objective groundu of its self-determination is the end, and this, if it is given by mere reason, must hold equally for all rational beings. By contrast, what contains merely the ground of the possibility of an action the effect of which is an end is called the means. The subjective ground of desiring is the incentive, the objective ground of willing the motivating ground; hence the difference between subjective ends, which rest on incentives, and objective ones, which depend on motivating grounds that hold for every rational being. Practical principles are formal if they abstract from all subjective ends; they are material if they have these, and hence certain incentives, at their foundation. The ends that a rational being intends at its discretion as effects of its actions (material ends) are one and all only relative; for merely their relation to a particular kind of desiderative faculty of the subject gives them their worth, which can therefore furnish no universal principles that are valid as well as necessary for all rational beings, 4:428 or for all willing, i.e. practical laws. That is why all these relative ends are the ground of hypothetical imperatives only.
But suppose there were something the existence of which in itself has an absolute worth, that, as an end in itself, could be a ground of determinate laws, then the ground of a possible categorical imperative, i.e. of a practical law, would lie in it, and only in it alone.
Now I say: a human being and generally every rational being exists as an end in itself, not merely as a means for the discretionary use for this or that will, but must in all its actions, whether directed towards itself or also to other rational beings, always be considered at the same time as an end. All objects of inclinations have a conditional worth only; for if the inclinations, and the needs founded on them, did not exist, their object would be without worth. But the inclinations themselves, as sources of need, are so far from having an absolute worth – so as to make one wish for them as such – that to be entirely free from them must rather be the universal wish of every rational being. Therefore the worth of any object to be acquired by our action is always conditional. Beings whose existence rests not indeed on our will but on nature, if they are non-rational beings, still have only a relative worth, as means, and are therefore called things, whereas rational beings are called persons, because their nature already marks them out as ends in themselves, i.e. as something that may not be used merely as a means, and hence to that extent limits all choice (and is an object of respect). These are therefore not merely subjective ends, the existence of which, as the effect of our action, has a worth for us; but rather objective ends, i.e. entitiesv whose existence in itself is an end, an end such that no other end can be put in its place, for which they would do service merely as means, because without it nothing whatsoever of absolute worth could be found; but if all worth were conditional, and hence contingent, then for reason no supreme practical principle could be found at all.
If, then, there is to be a supreme practical principle and, with regard to the human will, a categorical imperative, it must be such that, from the representation of what is necessarily an end for everyone, because it is an end in itself, it constitutes an objective 4:429 principle of the will, and hence can serve as a universal practical law. The ground of this principle is: a rational naturew exists as an end in itself. That is how a human being by necessity represents his own existence; to that extent it is thus a subjective principle of human actions. But every other rational being also represents its existence in this way, as a consequence of just the same rational ground that also holds for me;* thus it is at the same time an objective principle from which, as a supreme practical ground, it must be possible to derive all laws of the will. The practical imperative will thus be the following: So act that you use humanity, in your own person as well as in the person of any other, always at the same time as an end, never merely as a means. Let us try to see whether this can be done.
To keep to the previous examples:
First, according to the concept of necessary duty to oneself, someone who is contemplating self-murderx will ask himself whether his action can be consistent with the idea of humanity, as an end in itself. If to escape from a troublesome condition he destroys himself, he makes use of a person, merely as a means, to preserving a bearable condition up to the end of life. But a human being is not a thing, hence not something that can be used merely as a means, but must in all his actions always be considered as an end in itself. Thus the human being in my own person is not at my disposal, so as to maim, to corrupt, or to kill him. (I must here pass over the closer determination of this principle, needed to avoid any misunderstanding, e.g. of amputating limbs to preserve myself, of putting my life in danger to preserve my life, etc.; that belongs to actual moral science.)
Secondly, as far as necessary or owed duty to others is concerned, someone who has it in mind to make a lying promise to others will see at once that he wants to make use of another human being merely as a means, who does not at the same time contain in himself the end. For the one I want to use for my purposes by such a promise cannot possibly agree to my way of 4:430 proceeding with him and thus himself contain the end of this action. This conflict with the principle of other human beings can be seen more distinctly if one introduces examples of attacks on the freedom and property of others. For then it is clear that the transgressor of the rights of human beings is disposed to make use of the person of others merely as a means, without taking into consideration that, as rational beings, they are always to be esteemed at the same time as ends, i.e. only as beings who must, of just the same action, also be able to contain in themselves the end.*
Thirdly, with regard to contingent (meritorious) duty to oneself it is not enough that the action not conflict with humanity in our person, as an end in itself, it must also harmonize with it. Now there are in humanity predispositions to greater perfection, which belong to the end of nature with regard to humanity in our subject; to neglect these would perhaps be consistent with the preservation of humanity, as an end in itself, but not with the advancement of this end.y
Fourthly, as concerns meritorious duty to others, the natural end that all human beings have is their own happiness. Now, humanity could indeed subsist if no one contributed anything to the happiness of others while not intentionally detracting anything from it; but this is still only a negative and not positive agreement with humanity, as an end in itself, if everyone does not also try, as far as he can, to advance the ends of others. For if that representation is to have its full effect in me, the ends of a subject that is an end in itself must, as much as possible, also be my ends.