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.

Thus the principle that every human will is a will which in all
its maxims gives universal laws, * provided it be otherwise
justified, would be very well adapted to be the categorical
imperative, in this respect, namely, that just because of the idea
of universal legislation it is not based on interest, and therefore it
alone among all possible imperatives can be unconditional. Or still
better, converting the proposition, if there is a categorical
imperative (i.e., a law for the will of every rational being), it
can only command that everything be done from maxims of one's will
regarded as a will which could at the same time will that it should
itself give universal laws, for in that case only the practical
principle and the imperative which it obeys are unconditional, since
they cannot be based on any interest.



* I may be excused from adducing examples to elucidate this
principle, as those which have already been used to elucidate the
categorical imperative and its formula would all serve for the like
purpose here.