The exercise of reason in human acts and for the course of human fulfilment in Francisco Suárez, SJ (1548-1617) is intertwined or codetermined with other factors or dimensions of human subjectivity. Reason is not merely superstante, for it does not operate alone and apart from other internal configurations such as the affections and the teleology or directional tension that they articulate in human praxis. On the disposition of the affections that operate in the exercise of the will, configuring human subjectivity in relation to itself and in the environment of its fundamental relations, the others, the whole of creation and with God, will depend the correct use of reason in the process of its personal realisation and before the othernesses to which it responds. The wisdom of medieval and patristic mystical theology is present in Suárez’s thought and in the Jesuit spiritual tradition to show and take charge of the richness and complexity of the homo interior. The mystical core of human subjectivity must be reflexively considered and cared for, since the ethicity and the communitarian and political sociability of the human being depend on its configuration.