During my time as a law tutor, it became increasingly difficult to teach the Roman law of slavery. The closest I can come to explaining how resistance to the subject grew is that students regarded it as a kind of courtier’s discipline. Why pay attention to the writings of the Roman jurists on, say, the recovery of debts against a master for the actions of his slave, when the whole institution of slavery is a moral disgrace? It’s like hearing out a manservant’s mutterings on the exquisite lacing of the emperor’s new clothes when, in fact, he’s naked.

The problem with this view is that the jurists gave us the most sophisticated account of slavery in any historic civilisation. By studying it we learn, for instance, how the moral system of the Romans differed from our own. We learn how a slave society tries—and fails—to replicate the institutions of a free society, or how it responds to commercial challenges and social changes. Given the market sophistication of Ancient Rome and the level of education and wealth attained by many urban slaves, for example, a scholar of Roman law can question the limits of a Panglossian liberalism which suggests civil freedoms must naturally follow from economic liberty.

We also learn that the rule of law is older than liberalism, and that the two civilisations from whence it first emerged—Classical Rome and Medieval and Early Modern England—were not liberal societies. While it is true that England later evolved into a liberal civilisation—exporting various forms of liberalism globally—the Romans backslid both legally and institutionally as their Empire came under stress during the Crisis of the Third century.

The Corpus Iuris Civilis was found mouldering in the stacks at Bologna University library some 600 years after the fall of the Western Empire, and it only began to exert renewed influence on Western Europe from that point. English legal achievements came about independently of any Roman ones for the simple reason that for much of their history the English did not have access to the earlier civilisation’s legal knowledge and development. An English abbey’s library would have a hand-written copy—sometimes several—of the Aeneid and Metamorphoses, two great works of Roman literature that, if written today, would go in the stacks marked “fiction” or “poetry.” Meanwhile, “Ulpian” and “Gaius”—two of the greatest Roman jurists—were no more than names from a long-ago time, if that.

Neither legal system emerged fully formed, either. Standard English and Roman legal histories show societies spending centuries working out things that seem obvious to modern lawyers and even many non-lawyers. One of the reasons Cicero is not accounted a great Roman jurist but much later figures are considered such is because Roman trials were, as the kids say, “absolutely wild.” They routinely violated basic modern legal principles: flagrant appeals to emotion, nasty character attacks, outrageous counteraccusations to deflect blame—all without what a modern court would consider reliable evidence. Notoriously, elite testimony was preferred over that of commoners and Romans generally over foreigners, while slaves were often subjected to court-ordered torture.

The same pattern repeats in England, sometimes in discomforting ways. English law underwent serious Roman-style backsliding during the Cromwellian Interregnum, complicating the great parliamentarian’s historic legacy in ways that are not often known among non-lawyers.