 Second, Aquinas grounds the norms for these exchanges in the ancient formula of Justinian, which hearkens back to Plato: justice is giving each his own. But his interpretation of this formula situates him astride a deep but subtle divide between ancient and modern thought. To some extent this effect is an upshot of his inheriting not only the Greek eudaimonist tradition, but also a Roman jurisprudential tradition in which notions like standing and right as claim (rather than, say, fairness) had begun to emerge (Porter 2016, p. 143). As a result, Aquinas’ synergistic account has some novel complications.