This book explores the place of intellect and intellectual virtue in Aristotle’s moral and political thought by means of a close, thematically selective commentary on the Nicomachean Ethics. Special attention is given to the end or standard that reason looks to in guiding moral choice, the meaning of happiness (eudaimonia), the relation between theoretical wisdom (sophia) and active wisdom (phronesis), and the failures of reason in the phenomenon of the lapse of self control (akrasia). The book argues that Aristotelian moral theory is best understood as a two-pronged response to Socratic thought. The first part of this project is to respond to the Socratic paradox that virtue is knowledge with a sober, practically useful, and phenomenologically accurate account of moral virtue as a unique form of excellence rooted in the passions, cultivated through habituation, aimed at what is noble for its own sake, and guided by its own intellectual virtue, phronesis or active wisdom. This project gives to the moral life both dignity and guidance as Aristotle refines and improves traditional moral opinion, while defending moral responsibility. In the second part of the project Aristotle narrows the distance between his own and Socratic thought as he probes the deeper sources of human choices, shows the central role of understanding in true virtue, and explores problems with the active life that are ultimately resolved only in the theoretical life. In all of this he suggests a far closer connection than first appears between theoretical wisdom and active wisdom properly understood.