a practical proposition which does not deduce the willing of an action by mere analysis from another already presupposed (for we have not such a perfect will), but connects it immediately with the conception of the will of a rational being, as something not contained in it.] and as there is so much difficulty in discerning the possibility of speculative propositions of this kind, it may readily be supposed that the difficulty will be no less with the practical.

In this problem we will first inquire whether the mere conception of a categorical imperative may not perhaps supply us also with the formula of it, containing the proposition which alone can be a categorical imperative; for even if we know the tenor of such absolute command, yet how it is possible will require further special and laborious study, which we postpone to the last section.

When I conceive a hypothetical imperative in general I do not know beforehand what it will contain until I am given the condition.  But when I conceive a categorical imperative I know at once what it contains.  For as the imperative contains besides the law only the necessity that the maxims [Footnote:  A maxim is a subjective principle of action, and must be distinguished from the objective principle, namely, practical law.  The former contains the practical rule set by reason according to the conditions of the subject (often its ignorance or its inclinations), so that it is the principle on which the subject acts; but the law is the objective principle valid for every rational being, and is the principle on which it ought to act that is an imperative.] shall conform to this law, while the law contains no conditions restricting it, there remains nothing but the general statement that the maxim of the action should conform to a universal law, and it is this conformity alone that the imperative properly represents as necessary. [Footnote:  I have no doubt that “den” in the original before “Imperativ” is a misprint for “der,” and have translated accordingly.  Mr. Semple has done the same.  The editions that I have seen agree in reading “den,” and M. Barni so translates.  With this reading, it is the conformity that presents the imperative as necessary.]

There is therefore but one categorical imperative, namely this:  Act only on that maxim whereby thou canst at the same time will that it should become a universal law.

Now if all imperatives of duty can be deduced from this one imperative as from their principle, then, although it should remain undecided whether what is called duty is not merely a vain notion, yet at least we shall be able to show what we understand by it and what this notion means.

Since the universality of the law according to which effects are produced constiutes what is properly called nature in the most general sense (as to form), that is the existence of things so far as it is determined by general laws, the imperative of duty may be expressed thus:  Act as if the maxim of thy action were to become by thy will a Universal Law of Nature.