A good place to begin this chapter – and indeed this entire volume on republican values – is with the rubric De statu hominis from the opening of the Digest of Roman law, perhaps the most influential of all the classical discussions of the concept of civil liberty. There we read that ‘the fundamental division within the law of persons is that all men and women are either free or are slaves’. After this we are offered a formal definition of the concept of slavery. ‘Slavery is an institution of the ius gentium by which someone is, contrary to nature, subjected to the dominion of someone else.’ This in turn is said to yield a definition of individual liberty. If everyone in a civil association is either bond or free, then a civis or free subject must be someone who is not under the dominion of anyone else, but is sui iuris, capable of acting in their own right. It likewise follows that what it means for someone to lack the status of a free subject must be for that person not to be sui iuris but instead to be sub potestate, under the power or subject to the will of someone else.

While this summary was exceptionally influential, we already encounter a very similar analysis at a much earlier date among the historians and philosophers of ancient Rome, and especially in the writings of Cicero, Sallust, Livy and Tacitus.