This article discusses Aquinas' reception of the Augustinian distinction between ratio inferior and superior. Though not a central aspect of Aquinas' thought, it is a significant pointer to the presence of Augustinian patterns of thought in a non-theological part of his work. After a general survey of the presence of this distinction in the opera omnia of Aquinas, his use of this topic in some specific instances is discussed: the distinction between contemplative and active life, the division of human faculties, and the moral problem of peevish delight.