1. He who would portray the future of international law must first of all be exact in his attitude towards its past and present. International law as the law of the international community of states, such as is the present-day conception of it, is of comparatively modern origin. Science dutifully traces it back to Hugo Grotius as its father. In his immortal work on the Law of War and of Peace he, with masterly touch, focalizes (as it were) all the tendencies which asserted themselves during the latter half of the middle ages into a law between independent states, in such sort that all subsequent development goes back to him. Undoubtedly the roots of this law reach back into the remotest past of civilization, for independent states, nay, independent tribes too, cannot have more or less frequent dealings with each other without developing definite forms therefor. And so the immunity which must everywhere be conceded to ambassadors and heralds will probably be the oldest root of international law.

2. But all attempts to find in the ancient world a law of the same kind as modern international law must inevitably come to grief on the fact that the idea of a community of law between civilized states was entirely foreign to antiquity, and only begins to make its gradual appearance in the last third of the middle ages. The Jewish ideal of perpetual peace and the union of all mankind under One God, foreseen in prophetic vision by Isaiah (i-4), may be taken as the first formulation of pacificist doctrine, which of course implies a community of law between all states, but the prophet does not apprehend this community of law as an independent idea. This idea was likewise unknown in its generality to Greek civilization, although certainly looming before it with some clearness in the international relations of the Greek city-states one to another. But even if we may speak of a law resembling in many respects modern international law as prevailing between the states of ancient Greece, this law must nevertheless be limited to Greek states, foreign states and peoples standing outside this community of law as barbarians. On the other hand, Roman law possessed, it is true, a mass of legal rules for the intercourse between the Roman Empire and all foreign states, but these rules were Roman law and not rules of an international law such as postulates an international community of law.

3. The idea of an international community of law could not have obtained acceptance before a time when there existed a number of completely independent states, internally akin in virtue of a community of intensive civilization and continually brought into contact with one another by a lively intercourse. It was in this way that an international community of law was begotten at the end of the middle ages out of Christian civilization and mutual intercourse. Grotius and his forerunners would not have been able to create international law, had not the conception of a community of law between Christian states enjoyed a general recognition, and had not international intercourse before their day evolved already a large number of rules of intercourse, which were based on custom and in part on very ancient usages.

4. A theoretical basis for the erection of a system of international law was provided by the law of nature. This likewise is duteously traced back by science to Grotius, although in this department also he stands on the shoulders of his predecessors. The riddle, how it was possible to find a foundation for international law (as also for constitutional law and other branches of law) in the law of nature, which itself reposed upon so unstable a basis, is easy of solution for those who contemplate the historical development of all law with minds clear from prejudice. The contention of the historical school that all law springs up ‘naturally’, like language, is chimerical. Wherever a demand for law and order imperiously asserts itself, rules of law arise there. Every epoch of history produces alike that mode of legal development which it needs and that theoretical basis therefor which corresponds to its own interpretation of the nature of things. Accordingly the growth of law is everywhere dependent on, or at least influenced by, a conscious or unconscious creation of law. Custom, usage, habit, religion, morality, the nature of the thing, tradition, reason, the examples of single individuals, and many other factors, contribute the material out of which the requisite rules of law are built up. Where a strong central authority busies itself, year in year out, with legislation, expressly enacted law naturally takes the foremost place, and customary law makes itself felt to a less and less degree. But where such a strong central authority does not exist or does not busy itself with continuous legislation, then the above-named factors exercise a more direct influence upon the development of law, should there arise in actual life an imperious demand for definite rules of law. The theory of natural law was only the mirror held up by legal philosophy, in which the rays emitted by these factors were focused into a homogeneous image.

5. That, by the side of his international law, with its basis in natural law, there was also a positive international law, was not unrecognized by Grotius, but his purpose was merely to depict a system of international law which should compel universal observance irrespective of time and nation. And shortly after Grotius, Zouche and his followers did indeed attempt, in opposition to him, to formulate just such a positive international law, but it could not win for itself, at any rate in the seventeenth century, any great recognition; development was overshadowed by the system of Grotius, and many of his rules of natural law gradually obtained recognition in practice as customary law. But the increasing intercourse of states in the eighteenth century called forth a more positive school of international jurists, and the works of Bynkershoek, Moser, and Martens fertilized the soil on which in the nineteenth century there could gradually grow a really positive theory of international law, even if the scales which betoken its past connexion with natural law still adhere to the international law of to-day.

6. A positive theory of international law was demanded by the fact that in the first quarter of the nineteenth century, with the Final Act of the Congress of Vienna, the quasi-legislative activity of international conventions asserted itself for the first time. From then onwards, general international law was frequently evolved by means of an international convention. It was in this way that the permanent neutralization of Switzerland, Belgium, and Luxemburg was effected, the navigation of the so-called international rivers in Europe declared free, the slave-trade abolished, the grades of diplomatic agents regulated, privateering abolished, the necessity of effectiveness in a blockade recognized, the principle ‘free ships, free goods’ finally established, neutral goods on enemy ships declared free, rules provided in the interest of those wounded in battle, explosive bullets under the weight of 400 grammes forbidden, the Suez Canal neutralized, and so forth.

7. Another fact of great importance is the endeavour, which first manifested itself in the World Postal Union of 1874, to carry out the international administration of common interests, economic and other, by means of more or less general international unions. In this way a series of international administrative unions, often conjoined with special international boards, have been called into existence.

8. With the end of the nineteenth and the first decade of the twentieth century, in which occur the first and second Peace Conferences at The Hague and the Naval Conference of London, the development of international law enters upon a new and pregnant epoch. If hitherto, despite the momentous law-making treaties of the nineteenth century, international law was essentially a book-law, a system erected by greater or smaller authorities on the foundations of state practice and in its details often uncertain and contested, it is now subjected more and more, and in a wide domain, to the legislating influence of law-making international conventions. To mention only the principal matters: A code has been issued which, full of lacunae as it is, nevertheless encompasses the whole area of land war; it has been laid down that war shall only be begun by a declaration of war; the employment of force for the recovery of contract-debts has been forbidden; the rights and duties of neutrals in land war and naval war, the treatment of enemy merchant vessels at the outbreak of hostilities, and the conditions of the conversion of merchant vessels into men-of-war have been legislatively fixed; rules concerning the laying of submarine mines, concerning bombardment by naval forces in time of war, concerning the application of the principles of the Geneva Convention to naval warfare, concerning certain limitations on the right of prize in naval warfare have been agreed on; many states have concurred in a prohibition of the discharge of explosive missiles from air-ships; and a code of the rules of naval warfare, so far as it touches the trade of neutrals, dealing with the topics of blockade, contraband of war, unneutral service, destruction of neutral prizes, sale of enemy merchantmen to neutrals, enemy property, convoy and so forth, has been agreed on, though still unratified.

9. It is noteworthy that the first Hague Conference established a permanent international arbitral tribunal and that the second Hague Conference decided on the establishment of an International Prize Court and produced a plan for a standing international court at The Hague. Hitherto there have been no international courts for the decision of disputes, and if contending powers have been ready to refer their disputes to arbitration, they have always first had to form an arbitral tribunal; but now there is in existence an actual International Court of Arbitration, and other international courts are in contemplation.

10. Lastly, it is noteworthy that in the Final Act of the second Hague Conference a recommendation was expressed that the powers should call a third Conference in the year 1915, and two years before its meeting should appoint a preparatory committee, entrusted, among other things, with the task of proposing a system of organization and procedure for the coming Conference. This recommendation gives the first impetus towards making the Hague Conferences a permanent institution and so ensuring their periodic assembly without the need of initiative on the part of some one power or another.

11. Neither all the results of the second Hague Peace Conference nor those of the London Naval Conference are as yet assured, for the Declaration of London has not yet been ratified, and so the fate of the International Prize Court is still involved in doubt. The fate of some of the numerous conventions of the second Hague Conference is still in similar doubt, and many of those conventions which have been ratified present only a fragmentary and provisional settlement of their respective topics. Whatever may be the fate of these agreements which are still in suspense, this much is certain, that international legislation, international administration of justice, and international organization occupy the foreground of affairs, have already been in part established, and must be in ever-increasing requisition by the present and the coming generation.

12. If in the following pages I undertake the discussion of these three weighty matters, it is entirely foreign to my purpose to peer into the future with the eyes of prophecy or to busy my fancy with building castles in the air. What I propose is only to place in clear light the problems which are now coming into view and to furnish some indications which may contribute to their successful solution. If it is only to happy accident that we owe the assembling of the Peace Conferences, and likewise the issues of the same, we must all the more attempt in the future to assure success by dint of careful deliberation, systematic preparation, and a purposeful consideration of the problems which press for attention. And the science of international law must bethink itself and devote itself, with a more exact method than has hitherto been usual, to the elaboration of the results of past and future Conferences and to the incorporation of them in its system.