This book traces the history of Germanic mysticism from the nun Hildegard von Bingen to the founding of psychoanalysis. Its focal points are Meister Eckhart, Jacob Boehme, and Idealist philosophy. It takes its readers down what Hopkins called "cliffs of fall, frightful, sheer, no-man-fathomed": the nothingness of Eckhart's God beyond God, Boehme's Ungrund, and the spirit of the depths that Carl Jung termed the collective unconscious.