The Romans were endowed with a genius for law. Under the later Republic and the Empire, the minds of their jurists were trained and broadened by Greek philosophy and the study of the laws of Mediterranean peoples; Rome was becoming the commercial as well as social and political centre of the world. From this happy combination of causes resulted the most comprehensive body of law and the noblest jurisprudence ever evolved by a people. The great jurisconsults of the Empire, working upon the prior labours of long lines of older praetors and jurists, perfected a body of law of well-nigh universal applicability, and throughout logically consistent with general principles of law and equity, recognized as fundamental. These were in part suggested by Greek philosophy, especially by Stoicism as adapted to the Roman temperament. They represented the best ethics, the best justice of the time. As principles of law, however, they would have hung in the air, had not the practical as well as theorizing genius of the jurisconsults been equal to the task of embodying them in legal propositions, and applying the latter to the decision of cases. Thus was evolved a body of practical rules of law, controlled, co-ordinated, and, as one may say, universalized through the constant logical employment of sound principles of legal justice.[343] The Roman law, broadly taken, was heterogeneous in origin, and complex in its modes of growth. The great jurisconsults of the Empire recognized its diversity of source, and distinguished its various characteristics accordingly. They assumed (and this was a pure assumption) that every civilized people lived under two kinds of law, the one its own, springing from some recognized law-making source within the community; the other the _jus gentium_, or the law inculcated among all peoples by natural reason or common needs. The supposed origin of the _jus gentium_ was not simple. Back in the time of the Republic it had become necessary to recognize a law for the many strangers in Rome, who were not entitled to the protection of Rome’s _jus civile_. The edict of the praetor Peregrinus covered their substantial rights, and sanctioned simple modes of sale and lease which did not observe the forms prescribed by the _jus civile_. So this edict became the chief source of the _jus gentium_ so-called, to wit, of those liberal rules of law which ignored the peculiar formalities of the stricter law of Rome. Probably foreign laws, that is to say, the commercial customs of the Mediterranean world, were in fact recognized; and their study led to a perception of elements common to the laws of many peoples. At all events, in course of time the _jus gentium_ came to be regarded as consisting of universal rules of law which all peoples might naturally follow.