The social and economic life of the ancient world was reared upon a substructure of slavery. The commercial greatness of Carthage, Tyre, and Babylon had depended on the same principle. Amid all the variety of notions and dominant ideas current in classical civilization there was one point of agreement. ‘It was universally assumed’, as Dr. A. N. Whitehead expresses it, ‘that a large slave population was required to perform services which were unworthy to engage the activities of a fully civilized man.’