 Augustine tells us that at the age of eighteen Cicero’s (now lost) protreptic dialogue Hortensius enflamed him for philosophy (Confessiones 3.7), that as a young man he read Aristotle’s Categories (ib. 4.28) and that his conversion was greatly furthered by his Neoplatonic readings (ib. 7.13) as well as by the letters of Paul (ib. 7.27; Contra Academicos 2.5). He is more reticent about Manichean texts, of which he must have known a great deal (van Oort 2012). From the 390s onwards the Bible becomes decisive for his thought, in particular Genesis, the Psalms and the Pauline and Johannine writings (even though his exegesis remains philosophically impregnated), and his mature doctrine of grace seems to have grown from a fresh reading of Paul ca. 395 (see  7.6 Grace, Predestination and Original Sin).