The Metaphysical Elements of Ethics · Immanuel Kant
III. Of the Reason for conceiving an End which is also a Duty
An end is an object of the free elective will, the idea of which determines this will to an action by which the object is produced. Accordingly every action has its end, and as no one can have an end without himself making the object of his elective will his end, hence to have some end of actions is an act of the freedom of the agent, not an affect of physical nature. Now, since this act which determines an end is a practical principle which commands not the means (therefore not conditionally) but the end itself (therefore unconditionally), hence it is a categorical imperative of pure practical reason and one, therefore, which combines a concept of duty with that of an end in general. Now there must be such an end and a categorical imperative corresponding to it. For since there are free actions, there must also be ends to which as an object those actions are directed. Amongst these ends there must also be some which are at the same time (that is, by their very notion) duties. For if there were none such, then since no actions can be without an end, all ends which practical reason might have would be valid only as means to other ends, and a categorical imperative would be impossible; a supposition which destroys all moral philosophy.
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