capability of the maxims of every good will to make themselves a universal law, is itself the only law which the will of every rational being imposes on itself, without needing to assume any spring or interest as a foundation.

How such a synthetical practical a priori proposition is possible, and why it is necessary, is a problem whose solution does not lie within the bounds of the metaphysic of morals; and we have not here affirmed its truth, much less professed to have a proof of it in our power. We simply showed by the development of the universally received notion of morality that an autonomy of the will is inevitably connected with it, or rather is its foundation.

Whoever then holds morality to be anything real, and not a chimerical idea without any truth, must likewise admit the