Henry David Thoreau is famous for the literary excellence of his political and nature writings but his friend Harrison Blake understood that the significance of Thoreau's life was in fact spiritual, and he asked him for guidance in finding a path of his own. The result was a regular exchange of letters charting the evolution of Thoreau as a writer and thinker. The fifty letters, assembled and annotated here are by turns earnest, oracular, witty, playful, practical, insightful and inspiring.