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46 Institutional Treatise published under the authority of the Emperor Justinian, "who are ruled by laws and customs, are governed partly by their own particular laws, and partly by those laws which are common to all mankind. The law which a people enacts is called the Civil Law of that people, but that which natural reason appoints for all mankind is called the Law of Nations, because all nations use it." The part of the law "which natural reason appoints for all mankind" was the element which the Edict of the Prætor was supposed to have worked into Roman jurisprudence. Elsewhere it is styled more simply Jus Naturale, or the Law of Nature; and its ordinances are said to be dictated by Natural Equity (naturalis æquitas) as well as by natural reason. I shall attempt to discover the origin of these famous phrases, Law of Nations, Law of Nature, Equity, and to determine how the conceptions which they indicate are related to one another.

The most superficial student of Roman history must be struck by the extraordinary degree in which the fortunes of the republic were affected by the presence of foreigners, under different names, on her soil. The causes of this immigration are discernible enough at a later period, for we can readily understand why men of all races should flock to the mistress of the world; but the same phenomenon of a large population of foreigners and denizens meets us in