This violation of the principle of humanity in other men is more obvious if we take in examples of attacks on the freedom and property of others. For then it is clear that he who transgresses the rights of men intends to use the person of others merely as a means, without considering that as rational beings they ought always to be esteemed also as ends, that is, as beings who must be capable of containing in themselves the end of the very same action.**Let it not be thought that the common "quod tibi non vis fieri, etc." could serve here as the rule or principle. For it is only a deduction from the former, though with several limitations; it cannot be a universal law, for it does not contain the principle of duties to oneself, nor of the duties of benevolence to others (for many a one would gladly consent that others should not benefit him, provided only that he might be excused from showing benevolence to them), nor finally that of duties of strict obligation to one another, for on this principle the criminal might argue against the judge who punishes him, and so on.
Thirdly, as regards contingent (meritorious) duties to oneself: It is not enough that the action does not violate humanity in our own person as an end in itself, it must also harmonize with it. Now there are in humanity capacities of greater perfection, which belong to the end that nature has in view in regard to humanity in ourselves as the subject: to neglect these might perhaps be consistent with the maintenance of humanity as an end in itself, but not with the advancement of this end.
Fourthly, as regards meritorious duties towards others: The natural end which all men have is their own happiness. Now humanity might indeed subsist, although no one should contribute anything to the happiness of others, provided he did not intentionally withdraw anything from it; but after all this would only harmonize negatively not positively with humanity as an end in itself, if every one does not also endeavour, as far as in him lies, to forward the ends of others. For the ends of any subject which is an end in himself ought as far as possible to be my ends also, if that conception is to have its full effect with me.
This principle, that humanity and generally every rational nature is an end in itself (which is the supreme limiting condition of every man's freedom of action), is not borrowed from experience, firstly, because it is universal, applying as it does to all rational beings whatever, and experience is not capable of determining anything about them; secondly, because it does not present humanity as an end to men (subjectively), that is as an object which men do of themselves actually adopt as an end; but as an objective end, which must as a law constitute the supreme limiting condition of all our subjective ends, let them be what we will; it must therefore spring from pure reason. In fact the objective principle of all practical legislation lies (according to the first principle) in the rule and its form of universality which makes it capable of being a law (say, e. g., a law of nature); but the subjective principle is in the end; now by the second principle the subject of all ends is each rational being, inasmuch as it is an end in itself. Hence follows the third practical principle of the will, which is the ultimate condition of its harmony with universal practical reason, viz.: the idea of the will of every rational being as a universally legislative will.
On this principle all maxims are rejected which are inconsistent with the will being itself universal legislator. Thus the will is not subject simply to the law, but so subject that it must be regarded as itself giving the law and, on this ground only, subject to the law (of which it can regard itself as the author).
In the previous imperatives, namely, that based on the conception of the conformity of actions to general laws, as in a physical system of nature, and that based on the universal prerogative of rational beings as ends in themselves- these imperatives, just because they were conceived as categorical, excluded from any share in their authority all admixture of any interest as a spring of action; they were, however, only assumed to be categorical, because such an assumption was necessary to explain the conception of duty. But we could not prove independently that there are practical propositions which command categorically, nor can it be proved in this section; one thing, however, could be done, namely, to indicate in the imperative itself, by some determinate expression, that in the case of volition from duty all interest is renounced, which is the specific criterion of categorical as distinguished from hypothetical imperatives. This is done in the present (third) formula of the principle, namely, in the idea of the will of every rational being as a universally legislating will.
For although a will which is subject to laws may be attached to this law by means of an interest, yet a will which is itself a supreme lawgiver so far as it is such cannot possibly depend on any interest, since a will so dependent would itself still need another law restricting the interest of its self-love by the condition that it should be valid as universal law.
