Natural law is a crucial subject in the twelfth-century debates among Roman and canon lawyers, but also among the exegetes and theologians. Starting from two verses of Paul’s Epistle to the Romans (Rm 1:18-20 and 2:13-14), the masters debated the natural capability of human being to achieve a moral knowledge and the features of the universal moral principle, that is the lex naturalis, which natural reason can understand. Through the analysis of Gilbert of La Porrée’s Glossa in epistolas Beati Pauli (ca. 1130) and of Ps. Hugh of St. Victor’s Quaestiones in epistolas Beati Pauli (ca. 1160), this essay examines the exegetical developments in the Parisian milieu of the mid-twelfth century. It shows how the doctrinal positions of Gilbert and the...