In view of the background provided in the previous chapter, the present chapter will outline the Summa’s account of the Trinity, which can be found at the end of the first volume of the Summa Halensis. This is succeeded only by a final treatise of approximately 250 pages on the divine names (de divinis nominibus) which further elaborates the Summa’s doctrine of God as three-in-one.1 As one of the first treatises entailing a commentary of sorts on Pseudo-Dionysius’ De divinis nominibus, the presence of this treatise in the Summa signifies the attraction of the Greek Father to the early Franciscans. In addition to Pseudo-Dionysius, John of Damascus remains a key authority throughout the Summa’s discussion of the Trinity, along with Augustine and Richard of St Victor.