This paper explores some presuppositions in Francisco Suarez's theory of law. I intend to show that his doctrine of law can be understood more deeply attending to the role the intellect and the will play in its genesis, i.e. I intend to construct a view of the grounding of the law in the moral psychology of Francisco Suarez. The interaction between the intellect and the will make way for the recognition of the goodness of beings and the openness of human nature to formulate different practical courses of action and to self-determine itself towards those concrete forms of goodness. A comparison with the animal-sensitive circuit of action will be offered as a contrast.