Justice is the set and constant purpose which gives to every man his due.

1 Jurisprudence is the knowledge of things divine and human, the science of the just and the unjust.

2 Having laid down these general definitions, and our object being the exposition of the law of the Roman people, we think that the most advantageous plan will be to commence with an easy and simple path, and then to proceed to details with a most careful and scrupulous exactness of interpretation. Otherwise, if we begin by burdening the student's memory, as yet weak and untrained, with a multitude and variety of matters, one of two things will happen: either we shall cause him wholly to desert the study of law, or else we shall bring him at last, after great labour, and often, too, distrustful of his own powers (the commonest cause, among the young, of ill-success), to a point which he might have reached earlier, without such labour and confident in himself, had he been led along a smoother path.

3 The precepts of the law are these: to live honestly, to injure no one, and to give every man his due.

4 The study of law consists of two branches, law public, and law private. The former relates to the welfare of the Roman State; the latter to the advantage of the individual citizen. Of private law then we may say that it is of threefold origin, being collected from the precepts of nature, from those of the law of nations, or from those of the civil law of Rome.