"Great is the force of love, wondrous is its strength. Many are the degrees of love . . . and who can worthily distinguish among them?" cried the twelfth-century cleric, Richard of St. Victor. What relationships, human and divine, are appropriate to this protean creature, man with his great gifts and imperative appetites? The different answers given this question by the monks and scholars, the courtly poets and bawdy ballad writers of medieval...