In modern days the name of International Law has been very much confined to rules laid down by one particular class of writers. They may be roughly said to begin in the first half of the seventeenth century . . . It is further to be noted that before international law fell into the hands of these writers it had like most other subjects of thought attracted the attention of the Church. There is a whole chapter of the law of nations which is treated of by Roman Catholic theological writers, and a slight difference which distinguishes their use of technical expressions, such for example as 'law of nature' and 'natural law,' occasionally perplexes the student of the system before us. * * * Hence it came about that the great international jurists belonged to the smaller states and were wholly Protestants. . . . A law with a new sanction was required if states were to obey it, and this is what the new jurists produced. The effect was a rapid mitigation of wars and a rapid decrease in their frequency. * * * We may answer pretty confidently that its rapid advance to acceptance by civilised nations was a stage, though a very late stage, in the diffusion of Roman Law over Europe. * * * A great part, then, of International Law is Roman Law, spread over Europe by a process exceedingly like that which, a few centuries earlier, had caused other portions of Roman Law to filter into the interstices of every European legal system. The Roman element in International Law belonged, however, to one special province of the Roman system, that which the Romans themselves called Natural Law or, by an alternative name, Jus Gentium. * * * But though the founders of the system which lies at the basis of the rules now regulating the concerns of states inter se were not the first to describe the Law of Nature and the Law of Nations, Jus Nature, Jus Gentium, as the most admirable, the most dignified portion of Roman Law, they speak of it with a precision and a confidence which were altogether new. * * * It is sometimes difficult to be quite sure how Grotius and his successors distinguished rules of the Law of Nature from religious rules prescribed by inspired writers. But that they did draw a distinction is plain. Grotius's famous work, the 'De Jure Belli et Pacis,' is in great part composed of examples supplied by the language and conduct of heathen statesmen, generals, and sovereigns, whom he could not have supposed to know anything of inspired teaching. If we assume him to have believed that the most humane and virtuous of the acts and opinions which he quotes were prompted by an instinct derived from a happier state of the human race, when it was still more directly shaped and guided by Divine authority, we should probably have got as near his conception as possible. * * * To each successive inquirer, the actual childhood of the human race looks less and less like the picture which the jurists of the seventeenth century formed of it. It was excessively inhuman in war; and it was before all things enamoured of legal technicality in peace. But nevertheless the system founded on an imaginary reconstruction of it more and more calmed the fury of angry belligerency, and supplied a framework to which more advanced principles of humanity and convenience easily adjusted themselves.