9. The unwritten law is that which usage has established; for ancient customs, being sanctioned by the consent of those who adopt them, are like laws.
10. The civil law is not improperly divided into two kinds, for the division seems to have had its origin in the customs of the two states, Athens and Lacedaemon. For in these states it used to be the case, that the Lacedaemonians rather committed to memory what they observed as law, while the Athenians rather observed as law what they had consigned to writing, and included in the body of their laws.
11. The laws of nature, which all nations observe alike, being established by a divine providence, remain ever fixed and immutable. But the laws which every state has enacted, undergo frequent changes, either by the tacit consent of the people, or by a new law being subsequently passed.
III. The Law of Persons.
All our law relates either to persons, or to things, or to actions. Let us first speak of persons; as it is of little purpose to know the law, if we do not know the persons for whose sake the law was made. The chief division in the rights of persons is this: men are all either free or slaves.
1. Freedom, from which men are said to be free, is the natural power of doing what we each please, unless prevented by force or by law.
2. Slavery is an institution of the law of nations, by which one man is made the property of another, contrary to natural right.
3. Slaves are denominated servi, because generals order their captives to be sold, and thus preserve them, and do not put them to death. Slaves are also called mancipia, because they are taken from the enemy by the strong hand.
4. Slaves either are born or become so. They are born so when their mother is a slave; they become so either by the law of nations, that is, by captivity, or by the civil law, as when a free person, above the age of twenty, suffers himself to be sold, that he may share the price given for him.
5. In the condition of slaves there is no distinction; but there are many distinctions among free persons; for they are either born free, or have been set free.
IV. The Free-born.
A person is ingenuus who is free from the moment of his birth, by being born in matrimony, of parents who have been either both born free, or both made free, or one of whom has been born and the other made free; and when the mother is free, and the father a slave, the child nevertheless is born free; just as he is if his mother is free, and it is uncertain who is his father; for he had then no legal father.
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