These are true principles making for the consistent development of a body of law. Observe the scope and penetration of some other general rules: “Nuptias non concubitus, sed consensus facit.”[351] This goes to the legal root of the whole conception of matrimony, and is still the recognized starting-point of all law upon that subject. Again: “An agreement to perform what is impossible will not sustain a suit.”[352] This is still everywhere a fundamental principle of the law of contracts. Again: “No one can transfer to another a greater right than he would have himself,”[353] another principle of fundamental validity, but, of course, like all rules of law subject in its application to the qualifying operation of other legal rules. Roman jurisprudence recognized the danger of definition: “Omnis definitio in jure civili periculosa est.”[354] Yet it could formulate admirable ones; for example: “Inheritance is succession to the sum total (_universum jus_) of the rights of the deceased.”[355] This definition excels in the completeness of its legal view of the matter, and is not injured by the obvious omission to exclude those personal privileges and rights of the deceased which terminate upon his death. Thus we note the sources and constructive principles of the Roman law. We observe that while certain of the former might be called “statutory,” the chief means and method of development was the declarative edict of the praetor and the trained labour of the jurisconsults. In these appears the consummate genius of Roman jurisprudence, a jurisprudence matchless in its rational conception of principles of justice which were rooted in a philosophic consideration of human life; matchless also in its carrying through of such principles into the body of the law and the decision of every case. II The Roman law was the creation of the genius of Rome and also the product of the complex civilization of which Rome was the kinetic centre. As the Roman power crumbled, Teutonic invaders established kingdoms within territories formerly subject to Rome and to her law--a law, however, which commonly had been modified to suit the peoples of the provinces. Those territories retained their population of provincials. The invaders, Burgundians, Visigoths, and Franks, planting themselves in the different parts of Gaul, brought their own law, under which they continued to live, but which they did not force upon the provincial population. On the contrary, Burgundian and Visigothic kings promulgated codes of Roman law for the latter. And these represent the forms in which the Roman law first passed over into modes of acceptance and application no longer fully Roman, but partly Teutonic and incipiently mediaeval. They exemplify, moreover, the fact, so many aspects of which have been already noticed, of transitional and partly barbarized communities drawing from a greater past according to their simpler needs.