Can the medieval world still speak to the modern? The implicit answer in Bede Jarrett's remarkable work, Social Theories of the Middle Ages, is a resounding "yes." Fascinating as a purely historical study, it serves also to present the foundation whereby Christendom began to articulate the vision of a different kind of common life.

Embedded in medieval doctrines regarding law, women, Christendom, art - and especially just war, property, money-making, and education - are principles that we would well relearn in the present age. By rediscovering the inner structure of such a society, we...