The unique character of Roman law has been treated for centuries; hymns enough have been sung. My purpose is different: I restrict the problem to Roman classical law and therefore have intentionally added this adjective to the title. Roman private law—and I have only private law to consider here—is not the same throughout the thousand years of its history. Modern research distinguishes in the legislation of Justinian what belongs to the Byzantine epoch from what is genuinely classical. Secondly, we now know more about pre-classical law so that we are better able to contrast classical with archaic law. A third reason for a revision of our view is the developed study of the oriental, the cuneiform, law, and some new research in Greek law. Owing to this threefold progress we can try to sketch the unique character of Roman classical law in comparison with other laws. I discern three periods of Roman law: archaic (or pre-classical) up to 150 B.C., classical from 150 B.C. to A.D. 300, Byzantine (or post-classical) from A.D. 300 to 565. These are the usual periods, except that I carry back the classical period to 150 B.C. I know that there are transitions; but if we take the years 150 B.C. and A.D. 300, we shall roughly mark the turning points and have before us three distinct periods of Roman law.