Among the postulates which form the foundation of International Law, or of so much of it as retains the figure which it received from its original architects, there are two or three of pre-eminent importance. The first of all is expressed in the position that there is a determinable Law of Nature. Grotius and his successors took the assumption directly from the Romans, but they differed widely from the Roman jurisconsults and from each other in their ideas as to the mode of determination. The ambition of almost every Publicist who has flourished since the revival of letters has been to provide new and more manageable definitions of Nature and of her law, and it is indisputable that the conception in passing through the long series of writers on Public Law has gathered round it a large accretion, consisting of fragments of ideas derived from nearly every theory of ethics which has in its turn taken possession of the schools. Yet it is a remarkable proof of the essentially historical character of the conception that, after all the efforts which have been made to evolve the code of nature from the necessary characteristics of the natural state, so much of the result is just what it would have been if men had been satisfied to adopt the dicta of the Roman lawyers without questioning or reviewing them. Setting aside the Conventional or Treaty Law of Nations, it is surprising how large a part of the system is made up of pure Roman law. Wherever there is a doctrine of the jurisconsults affirmed by them to be in harmony with the Jus Gentium, the publicists have found a reason for borrowing it, however plainly it may bear the marks of a distinctively Roman origin. We may observe too that the derivative theories are afflicted with the weakness of the primary notion. In the majority of the Publicists, the mode of thought is still "mixed." In studying these writers, the great difficulty is always to discover whether they are discussing law or morality--whether the state of international relations they describe is actual or ideal--whether they lay down that which is, or that which, in their opinion, ought to be.