 The Salamancan theologians and their successors not only discussed and modified Thomist natural law but also referred to other sources with slightly different categorizations, such as the distinction between ius humanum and ius naturale vel divinum made by Isidore of Seville (Liber etymologiarum, lib. 5 c. 2–18, Isidori Hispalensis episcopi etymologiarum libro XX, 1833), cited in Decretum Gratiani (Friedberg [ed.], Corpus Iuris Canonici, vol. 1, 1–5) and discussed by Soto (Soto-DII I, qu. V, art. iii and iv). There were many further differences among them on natural law, as on law in general. For instance, with regard to whether law was an act of will or an act of intellect, some, like Soto, favored the intellect despite his early education in Nominalist-dominated Paris, where voluntarism, an emphasis on the will over the intellect, prevailed; others, like Suárez, gave some relevance to the will. Nevertheless, they were in agreement that the principles of natural law were inscribed in the heart of humans, so that “no human being can plead ignorance as an excuse”, as Soto put it (Soto-DII I, qu. I art. 4; translated in Hamilton 1963: 15). Suárez’s concept of law has been described as voluntarist, but reason still played a significant role in his thought. Reason diagnosed situations, identifying possible remedies; but the will implemented these measures. These deliberations happened within the context of immutable natural law, which Suárez believed was known through specific precepts. In addition, he held that individual virtue lay in following right reason. Reason’s dictates were unique to human beings, not impulses shared with animals. The laws common to many peoples, though not universal, made up the ius gentium. What may seem at first glance an acknowledgment of the moral competence of all human beings was also used to justify punishment, including war and enslavement, against peoples from other continents.