Ninety percent of the people in the Roman Empire worked the land. This is the number that most discussions of Rome skip past in their attention to the legions and the Colosseum and the philosophical schools, but it is the number that actually determined the empire’s possibilities. Everything else — the armies, the cities, the building programs, the literary culture — was built on the agricultural surplus generated by the rural majority that never appears in the histories because it was not writing them. Roman civilization was an agricultural civilization with sophisticated urban superstructure, and understanding the agriculture is understanding the base on which everything else rested.