That the proposition Everything contingent must have a cause may be evident to everyone from mere concepts is not to be denied; but then the concept of the contingent is already taken in such a way that it contains, not the category of modality (as something, the non existence of which can be thought), but that of relationb (as something that can only exist as the consequence of something else), and then it is, of course, an identical proposition: hat can only exist as a consequence has its cause.