“Nature, habit, and teaching,” says Aristotle, “are all needed.” Because flourishing, you see, doesn’t just require us to identify and then acquire all of these virtues—it requires that we have every one in the exact right amount. We have to be generous but not too generous, courageous but not too courageous, and so on. The toughest part of virtue ethics is identifying these amounts, and then precisely nailing each one. Aristotle called each of those maddeningly specific targets: “the mean.”
