De Trinitate is Richard's opus magnum. Based on meditation of the daily liturgy in St. Victor, where the Quicumque was sung, it is a profound contribution to Trinitarian theology, combining an Augustinian grasp of the oneness of God with an original analysis of 'God is love, therefore Trinity'. Richard develops his famous new definition of persona designed to fit both tenets and applicable to both God and man. The influential master in spirituality...