For centuries the most revered poem in the Western literary canon, Vergil's Aeneid celebrates the Roman virtue of pietas. In the preface to his English translation of the poem, John Dryden attempts to explain all that this virtue includes: "Piety alone," he writes, "comprehends the whole Duty of Man towards the Gods, towards his Country, and towards his Relations." Dryden's definition belongs to a dialogue about meaning that reflects...