The Metaphysics of Morals by Immanuel Kant Chapter 2 Page 77

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.

Looking back now on all previous attempts to discover the principle of morality, we need not wonder why they all failed.

It was seen that man was bound to laws by duty, but it was not observed that the laws to which he is subject are only those of his own giving, though at the same time they are universal, and that he is only bound to act in conformity with his own