IV. During the second part of the Middle Ages more and more independent States arose on the European continent, and during the fifteenth and sixteenth centuries the necessity for a Law of Nations made itself felt. A multitude of Sovereign States had now established themselves which, although they were absolutely independent of one another, were knitted together by constant commercial and other intercourse, by a common religion, and by the same moral principles. Gradually and almost unconsciously the conviction had grown upon these independent States that, in spite of everything which separated them, they formed a Community the intercourse of which was ruled by certain legal principles. International Law grew out of custom because it was a necessity according to the well-known rule _ubi societas ibi jus_, where there is a community of interests there must be law. The several independent States had thus gradually and unconsciously formed themselves into a Society, the afterwards so-called Family of Nations, or, in other words, a League of Nations. And no sooner had this League of Nations come into existence--and even some time before that date--than a number of schemes for the establishment of eternal peace made their appearance. The first of these schemes was that of the French lawyer _Pierre Dubois_, who, as early as 1305, in his work 'De recuperatione terre sancte,' proposed an alliance between all Christian Powers for the purpose of the maintenance of peace and the establishment of a permanent Court of Arbitration for the settlement of differences between members of the alliance. Another was that of _Antoine Marini_, the Chancellor of Podiebrad, King of Bohemia, who adopted the scheme in 1461. This scheme proposed the foundation of a Federal State to comprise all the existing Christian States and the establishment of a permanent Congress to be seated at Basle in Switzerland, this Congress to be the highest organ of the Federation. A third scheme was that of _Sully_, adopted by Henri IV of France, which, in 1603, proposed the division of Europe into fifteen States and the linking together of these into a Federation with a General Council as its highest organ. And a fourth scheme was that of _Emeric Crucee_, who, in 1623, proposed the establishment of a Union consisting not only of the Christian States but of all States of the world, with a General Council seated at Venice. And since that time many other schemes of similar kind have made their appearance, the enumeration and discussion of which is outside our present purpose. So much is certain that all these schemes were Utopian. Nevertheless, a League of Nations having once come into existence, International Law grew more and more, and when in 1625 Hugo Grotius published his immortal work on 'The Law of War and Peace,' the system of International Law offered in his work conquered the world and became the basis of all following development.