7 The edicts of the praetors too have no small legal authority, and these we are used to call the 'ius honorarium,' because those who occupy posts of honour in the state, in other words the magistrates, have given authority to this branch of law. The curule aediles also used to issue an edict relating to certain matters, which forms part of the ius honorarium. 8 The answers of those learned in the law are the opinions and views of persons authorized to determine and expound the law; for it was of old provided that certain persons should publicly interpret the laws, who were called jurisconsults, and whom the Emperor privileged to give formal answers. If they were unanimous the judge was forbidden by imperial constitution to depart from their opinion, so great was its authority. 9 The unwritten law is that which usage has approved: for ancient customs, when approved by consent of those who follow them, are like statute. 10 And this division of the civil law into two kinds seems not inappropriate, for it appears to have originated in the institutions of two states, namely Athens and Lacedaemon; it having been usual in the latter to commit to memory what was observed as law, while the Athenians observed only what they had made permanent in written statutes. 11 But the laws of nature, which are observed by all nations alike, are established, as it were, by divine providence, and remain ever fixed and immutable: but the municipal laws of each individual state are subject to frequent change, either by the tacit consent of the people, or by the subsequent enactment of another statute. 12 The whole of the law which we observe relates either to persons, or to things, or to actions. And first let us speak of persons: for it is useless to know the law without knowing the persons for whose sake it was established. TITLE III. OF THE LAW OF PERSONS In the law of persons, then, the first division is into free men and slaves. 1 Freedom, from which men are called free, is a man's natural power of doing what he pleases, so far as he is not prevented by force or law: 2 slavery is an institution of the law of nations, against nature subjecting one man to the dominion of another. 3 The name 'slave' is derived from the practice of generals to order the preservation and sale of captives, instead of killing them; hence they are also called mancipia, because they are taken from the enemy by the strong hand. 4 Slaves are either born so, their mothers being slaves themselves; or they become so, and this either by the law of nations, that is to say by capture in war, or by the civil law, as when a free man, over twenty years of age, collusively allows himself to be sold in order that he may share the purchase money. 5 The condition of all slaves is one and the same: in the conditions of free men there are many distinctions; to begin with, they are either free born, or made free. TITLE IV. OF MEN FREE BORN