This lecture is devoted to exploring the idea of moral virtue, chiefly in the second and third books of the Nicomachean Ethics. It is necessary, to begin with, to say a few words about the idea of virtue in general and its two subspecies in particular, moral and intellectual virtue, a division for which Aristotle himself is responsible. We then turn to consider what is probably the most famous part of Aristotle’s ethical teaching, that of virtue understood as a mean between two extremes—courage, for example, being a mean between the extreme of cowardice on the one hand, and recklessness on the other. We conclude with some remarks on Aristotle’s intriguing account of voluntary and involuntary actions, or what we might call moral responsibility.