OF THE TWO DOMINICANS William Peraldus (ca. 1200-1271) and Thomas Aquinas (1225-74), Peraldus is now barely known whereas Aquinas, canonized and a doctor of the Church, is one of the most persistent influences on Catholic philosophy and theology. During their lives, it was a different story. A decree required that every Dominican convent hold a copy of Peraldus’s Summa de vitiis et virtutibus in its library, and this work—as the number of extant manuscripts testifies—was widely diffused across the whole of Christian Europe.2