Fifty-five mystics or mystical theologians, ancient and modern, are represented, including: Origen, Augustine of Hippo, Hildegard of Bingen, Francis of Assisi, Bonaventure, Angela of Foligno, Catherine of Siena, the anonymous author of Cloud of Unknowing, Thomas a' Kempis, Teresa of Avila, John of the Cross, Francis de Sales, Therese of Lisieux, Elizabeth of the Trinity, Pierre Teilhard de Chardin, Thomas Merton, and Karl Rahner.