The present treatise is, however, nothing more than the investigation and establishment of the supreme principle of morality, and this alone constitutes a study complete in itself and one which ought to be kept apart from every other moral investigation. No doubt my conclusions on this weighty question, which has hitherto been very unsatisfactorily examined, would receive much light from the application of the same principle to the whole system, and would be greatly confirmed by the adequacy which it exhibits throughout; but I must forego this advantage, which indeed would be after all more gratifying than useful, since the easy applicability of a principle and its apparent adequacy give no very certain proof of its soundness, but rather inspire a certain partiality, which prevents us from examining and estimating it strictly in itself and without regard to consequences. I have adopted in this work the method which I think most suitable, proceeding analytically from common knowledge to the determination of its ultimate principle, and again descending synthetically from the examination of this principle and its sources to the common knowledge in which we find it employed. The division will, therefore, be as follows: 1 FIRST SECTION. Transition from the common rational knowledge of morality to the philosophical. 2 SECOND SECTION. Transition from popular moral philosophy to the metaphysic of morals. 3 THIRD SECTION. Final step from the metaphysic of morals to the critique of the pure practical reason. SEC_1 FIRST SECTION TRANSITION FROM THE COMMON RATIONAL KNOWLEDGE OF MORALITY TO THE PHILOSOPHICAL Nothing can possibly be conceived in the world, or even out of it,