Hence, in spite of Christianity and its early vision of a brotherhood of men, the history of the Middle Ages came nearer to a realization of the idea of perpetual war than was possible in ancient times. The tendency of the growth of Roman supremacy was to diminish the number of wars, along with the number of possible causes of racial friction. It united many nations in one great whole, and gave them, to a certain extent, a common culture and common interests; even, when this seemed prudent, a common right of citizenship. The fewer the number of boundaries, the less the likelihood of war. The establishment of great empires is of necessity a force, and a great and permanent force working on the side of peace. With the fall of Rome this guarantee was removed.
The Development of the New Science of International Law.
Out of the ruins of the old feudal system arose the modern state as a free independent unity. Private war between individuals or classes of society was now branded as a breach of the peace: it became the exclusive right of kings to appeal to force. War, wrote Gentilis[22] towards the end of sixteenth century, is the just or unjust conflict between states. Peace was now regarded as the normal condition of society. As a result of these great developments in which the name “state” acquired new meaning, jurisprudence freed itself from the trammelling conditions of mediæval Scholasticism. Men began to consider the problem of the rightfulness or wrongfulness of war, to question even the possibility of a war on rightful grounds. Out of theses new ideas—partly too as one of the fruits of the Reformation,[23]—arose the first consciously formulated principles of the science of international law, whose fuller, but not yet complete, development belongs to modern times.
From the beginning of history every age, every people has something to show here, be it only a rudimentary sense of justice in their dealings with one another. We may instance the Amphictyonic League in Greece which, while it had a merely Hellenic basis and was mainly a religious survival, shows the germ of some attempt at arbitration between Greek states. Among the Romans we have the jus feciale[24] and the jus gentium, as distinguished from the civil law of Rome, and certain military regulations about the taking of booty in war. Ambassadors were held inviolate in both countries; the formal declaration of war was never omitted. Many Roman writers held the necessity of a just cause for war. But nowhere do these considerations form the subject matter of a special science.
In the Middle Ages the development of these ideas received little encouragement. All laws are silent in the time of war,[25] and this was a period of war, both bloody and constant. There was no time to think of the right or wrong of anything. Moreover, the Church emphasised the lack of rights in unbelievers, and gave her blessing on their annihilation.[26] The whole Christian world was filled with the idea of a spiritual universal monarchy. Not such as that in the minds of Greek and Jew and Roman who had been able to picture international peace only under the form of a great national and exclusive empire. In this great Christian state there were to be no distinctions between nations; its sphere was bounded by the universe. But, here, there was no room or recognition for independent national states with equal and personal rights. This recognition, opposed by the Roman Church, is the real basis of international law. The Reformation was the means by which the personality of the peoples, the unity and independence of the state were first openly admitted. On this foundation, mainly at first in Protestant countries, the new science developed rapidly. Like the civil state and the Christian religion, international law may be called a peace institution.
Grotius, Puffendorf and Vattel.
In the beginning of the seventeenth century, Grotius laid the foundations of a code of universal law (De Jure Belli et Pacis, 1625) independent of differences of religion, in the hope that its recognition might simplify the intercourse between the newly formed nations. The primary object of this great work, written during the misery and horrors of the Thirty Years’ war, was expressly to draw attention to these evils and suggest some methods by which the severity of warfare might be mitigated. Grotius originally meant to explain only one chapter of the law of nations:[27] his book was to be called De Jure Belli, but there is scarcely any subject of international law which he leaves untouched. He obtained, moreover, a general recognition for the doctrine of the Law of Nature which exerted so strong an influence upon succeeding centuries; indeed, between these two sciences, as between international law and ethics, he draws no very sharp line of demarcation, although, on the whole, in spite of an unscientific, scholastic use of quotation from authorities, his treatment of the new field is clear and comprehensive. Grotius made the attempt to set up an ethical principle of right, in the stead of such doctrines of self-interest as had been held by many of the ancient writers. There was a law, he held, established in each state purely with a view to the interests of that state, but, besides this, there was another higher law in the interest of the whole society of nations. Its origin was divine; the reason of man commanded his obedience. This was what we call international law.[28]
Grotius distinctly holds, like Kant and Rousseau, and unlike Hobbes, that the state can never be regarded as a unity or institution separable from the people; the terms civitas, communitas, coetus, populus, he uses indiscriminately. But these nations, these independent units of society cannot live together side by side just as they like; they must recognise one another as members of a European society of states.[29] Law, he said, stands above force even in war, “which may only be begun to pursue the right;” and the beginning and manner of conduct of war rests on fixed laws and can be justified only in certain cases. War is not to be done away with: Grotius accepts it as fact,[30] (as Hobbes did later) as the natural method for settling the disputes which were bound constantly to arise between so many independent and sovereign nations. A terrible scourge it must ever remain, but as the only available form of legal procedure, it is sanctioned by the practice of states and not less by the law of nature and of nations. Grotius did not advance beyond this position. Every violation of the law of nations can be settled but in one way—by war, the force of the stronger.
The necessary distinction between law and ethics was drawn by Puffendorf,[31] a successor of Grotius who gave an outwardly systematic form to the doctrine of the great jurist, without adding to it either strength or completeness. His views, when they were not based upon the system of Grotius, were strongly influenced by the speculation of Hobbes, his chronological predecessor, to whom we shall have later occasion to refer. In the works of Vattel,[32] who was, next to Rousseau, the most celebrated of Swiss publicists, we find the theory of the customs and practice in war widely developed, and the necessity for humanising its methods and limiting its destructive effects upon neutral countries strongly emphasised. Grotius and Puffendorf, while they recommend acts of mercy, hold that there is legally no right which requires that a conquered enemy shall be spared. This is a matter of humanity alone. It is to the praise of Vattel that he did much to popularise among the highest and most powerful classes of society, ideas of humanity in warfare, and of the rights and obligations of nations. He is, moreover, the first to make a clear separation between this science and the Law of Nature. What, he asks, is international law as distinguished from the Law of Nature? What are the powers of a state and the duties of nations to one another? What are the causes of quarrel among nations, and what the means by which they can be settled without any sacrifice of dignity?
They are, in the first place, a friendly conciliatory attitude; and secondly, such means of settlement as mediation, arbitration and Peace Congresses. These are the refuges of a peace-loving nation, in cases where vital interests are not at stake. “Nature gives us no right to use force, except where mild and conciliatory measures are useless.” (Law