It is one which is foreign to philosophy. I mean the Mosaic Decalogue. Indeed the spelling “du sollt” in the above instance of a moral law, the first put forward by Kant, na�vely betrays this origin.

A conception, however, which can\ point to no other source than this, has no right, without undergoing further scrutiny, thus to force its way into philosophical Ethics. It will be rejected, until introduced by duly accredited proof. Thus on the threshold of the subject Kant makes his first petitio principii, and that no small one.

Our philosopher, then, by begging the question in his preface, simply assumes the conception of Moral Law as given and existing beyond all doubt; and he treats the closely related conception of Duty (page 8, R., p. 16) exactly in the same way.