ON DUTIES deserves more attention than it gets, and it rewards the attention it receives, because it deals with the question of the well-lived life in a clear, thoughtful, accessible, and compelling manner. Cicero believed On Duties to be his magnum opus, and much of history has agreed with him on this. Of On Duties, the French philosopher Voltaire wrote: "No one will ever write anything more wise, more true, or more useful." And Martin Luther, in his Table Talk says this of Cicero: "Let those who wish to see a true philosophy read Cicero. Cicero was a wise and...