It is a truism to say that the characteristics of a legal system, in the social and political not less than in the technical field, depend mainly on the nature of its sources of law. If we confine our attention to Roman law, we may state that its achievements, as well as its failures were the consequence of the ways by which it was formed and developed throughout its long history.

The importance of this statement is enhanced by the fact that the Roman attitude to sources of law was apparently different from that of most ancient and modern legal systems. In particular, customary rules are said to have had a greater part in the creation and development of Roman law than of other legal systems. It would be misleading, however, to presume that the sources of Roman law, and the role of custom among them, remained unchanged during the course of Roman history.

Accordingly, at the very outset two points emerge, which merit discussion: (1) What was the part of customary rules and statutes in the creation and development of Roman law; (2) Whether, or how far, their relation changed from one period to another.