This chapter summarizes what is known of Augustine's access to the text of the Nicomachean Ethics (N.E.) and, in general, Aristotle's naturalistic account of human agency and happiness. It considers the impact of the Aristotelian conception of eudaimonia on Augustine's own treatment of human beatitude. The appropriation of this Aristotelian notion of eudaimonia is already evident in Augustine's early philosophical dialogues. Yet, in the same works one also finds a transformation and extension of Aristotle's philosophical conception of happiness. The chapter provides a paradigmatic account of the role Aristotle's ethics played in Augustine's thought. Among Latin Christians of the fourth century, Aristotle's reputation was largely that of a dialectician. Aristotle provided the necessary ontological connection in N.E., where he establishes the nature of the highest human good on the foundation of a functional analysis of human nature in terms of the capacity for rational activity.