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.
Annas goes on to explore the Platonic idea that humankind's final end is "becoming like God"--an idea that is well known among the ancients but virtually ignored in modern interpretations. She also maintains that modern interpretations, beginning in the nineteenth century, have placed undue emphasis on the Republic, and have treated it too much as a political work, whereas the ancients rightly saw it as a continuation of Plato's ethical writings.