This study proceeds from an investigation of the significance of the Christian doctrine of creatio ex nihilo in some of the key components of St. Augustine's extended anti-Manichaean polemic. To a great extent, his devastating critique of the Manichaeans' world view, their conception of evil, and their most fundamental theological presuppositions relied heavily upon the affirmation that God ultimately created everything that exists from nothing. In broader terms, the study demonstrates how the doctrine of creatio ex nihilo provided Augustine with an effective means of defining the character of created being as finite and mutable, and drawing a crucial ontological distinction between the Divine Nature and that which God creates. Such teachings were operative in some of the key themes of Augustine's theology.