[Footnote 12: The importance of the fact that subjects of the Law of Nations are States exclusively is so great that I consider it necessary to emphasise it again and again throughout this work. See, for instance, below, §§ 289, 344, 384. It should, however, already be mentioned here that this assertion is even nowadays still sometimes contradicted; see, for instance, Kaufmann, "Die Rechtskraft des Internationalen Rechts" (1899), _passim_; Rehm in Z.V. I. (1907), p. 53; and Diena in R.G. XVI. pp. 57-76.]
[Sidenote: Equality an Inference from the Basis of International Law.]
§ 14. Since the Law of Nations is based on the common consent of States as sovereign communities, the member States of the Family of Nations are equal to each other as subjects of International Law. States are by their nature certainly not equal as regards power, extent, constitution, and the like. But as members of the community of nations they are equals, whatever differences between them may otherwise exist. This is a consequence of their sovereignty and of the fact that the Law of Nations is a law between, not above, the States.[13]
[Footnote 13: See below, §§ 115-116, where the legal equality of States in contradistinction to their political inequality is discussed, and where it will also be shown that not-full Sovereign States are not equals of full-Sovereign States.]
Hall, pp. 5-14--Maine, pp. 1-25--Lawrence, §§ 61-66--Phillimore, I. §§ 17-33--Twiss, I. §§ 82-103--Taylor, §§ 30-36--Westlake, I. pp. 14-19--Wheaton, § 15--Halleck, I. pp. 55-64--Ullmann, §§ 8-9--Heffter, § 3--Holtzendorff in Holtzendorff, I. pp. 79-158--Rivier, I. § 2--Nys, I. pp. 144-165--Bonfils, Nos. 45-63--Despagnet, Nos. 58-63--Pradier-Fodéré, I. Nos. 24-35--Mérignhac, I. pp. 79-113--Martens, I. § 43--Fiore, I. Nos. 224-238--Calvo, I. §§ 27-38--Bergbohm, "Staatsverträge und Gesetze als Quellen des Völkerrechts" (1877)--Jellinek, "Die rechtliche Natur der Staatsverträge" (1880)--Cavaglieri, "La consuetudine giuridica internazionale" (1907).
[Sidenote: Source in Contradistinction to Cause.]
§ 15. The different writers on the Law of Nations disagree widely with regard to kinds and numbers of sources of this law. The fact is that the term "source of law" is made use of in different meanings by the different writers on International Law, as on law in general. It seems to me that most writers confound the conception of "source" with that of "cause," and through this mistake come to a standpoint from which certain factors which influence the growth of International Law appear as sources of rules of the Law of Nations. This mistake can be avoided by going back to the meaning of the term "source" in general. Source means a spring or well, and has to be defined as the rising from the ground of a stream of water. When we see a stream of water and want to know whence it comes, we follow the stream upwards until we come to the spot where it rises naturally from the ground. On that spot, we say, is the source of the stream of water. We know very well that this source is not the cause of the existence of the stream of water. Source signifies only the natural rising of water from a certain spot of the ground, whatever natural causes there may be for that rising. If we apply the conception of source in this meaning to the term "source of law," the confusion of source with cause cannot arise. Just as we see streams of water running over the surface of the earth, so we see, as it were, streams of rules running over the area of law. And if we want to know whence these rules come, we have to follow these streams upwards until we come to their beginning. Where we find that such rules rise into existence, there is the source of them. Of course, rules of law do not rise from a spot on the ground as water does; they rise from facts in the historical development of a community. Thus in Great Britain a good many rules of law rise every year from Acts of Parliament. "Source of Law" is therefore the name for an historical fact out of which rules of conduct rise into existence and legal force.