This paper faces the projections of the moral philosophy of Cicero on medieval scholastic ethics; it examines the influence of Cicero’s writings dealing with treatment of the justificating way of moral behavior starting from natural human inclinations. First, the article analyses the philosophical elaboration of the theme in the field of ciceronian thinking. Second, already inside the frame of medieval elaborations, the article deals with projections of ciceronian tradition around natural human inclinations in their relations with moral life, in the philosophical developments of Thomas Aquinas about origins of virtue and natural law.