The text investigates the conception of the common good, of the law and of political prudence in the most important thinkers of Scholasticism of the modern age, grasping the premises in the nature-grace relationship (from both a noetic and an ontological point of view). In this way, the essay captures the relationship – in its foundational rather than genetic meaning – between public law categories and theological categories. In particular, if as regards political prudence its essential heterogeneity with respect to (modern) reasons of state is revealed; in relation to the common good, the question of the unity or duplicity of the ultimate goal comes to the fore. This problem is analyzed with reference to emblematic texts, and thought along the side of the juridical-political implications.