motivation, a form of the law of causation; in other words, it is the causation which is brought about by the medium of the understanding.

It is the sole demonstrable law to which the human will as such is subject. It means that every action can only take place in consequence of a sufficient motive. Like causality in general, it is a natural law. On the other hand, moral laws, apart from human institution, state ordinance, or religious doctrine, cannot rightly be assumed as existing without proof. Kant, therefore, by taking such laws for granted, is guilty of a petitio principii, which is all the bolder, in that he at once adds (page vi of the preface) that a moral law ought to imply “absolute necessity.” But “absolute necessity” is everywhere characterised by an inevitable chain of