Julia Annas here offers a fundamental reexamination of Plato's ethical thought by investigating the Middle Platonist perspective, which emerged at the end of Plato's own school, the Academy. She highlights the differences between ancient and modern assumptions about Plato's ethics - and stresses the need to be more critical about our own. One of these modern assumptions is the notion that the dialogues record the development of Plato's thought.

Annas shows how the Middle Platonists, by contrast, viewed the dialogues as multiple presentations of a single Platonic ethical philosophy, differing in form and purpose but ultimately coherent. They also read Plato's ethics as consistently defending the view that virtue is sufficient for happiness, and see it as converging in its main points with the ethics of the Stoics.