Libertas is one of the main concepts of public life in the Roman world. It has a public content when referring to the freedom of the Republic, and a private implication when it is opposed to slavery. Florentinus' definition of libertas is quite interesting, because it was given within the context of slavery, although it does not fit that scenario entirely. In fact, it seems more cogent with regard to the public concept of libertas. This contribution analyses this aspect in detail.