There are certain acts that the law neither enjoins nor forbids; it is in these that a slave finds opportunity to perform a benefit. So long as what he supplies is only that which is ordinarily required of a slave, it is a “service”; when he supplies more than a slave need do, it is a “benefit”; it ceases to be called a service when it passes over into the domain of friendly affection. There are certain things, as for instance food and clothing, which the master must supply to the slave; no one calls these benefits. But suppose the master is indulgent, gives him the education of a gentleman, has him taught the branches in which the freeborn are schooled — all this will be a benefit. Conversely, the same is true in the case of the slave. All that he does in excess of what is prescribed as the duty of a slave, what he supplies, not from obedience to authority, but from his own desire, will be a benefit, provided that its importance, if another person were supplying it, would entitle it to that name.