Though not a professional philosopher, Henry David Thoreau is recognized as an important contributor to the American literary and philosophical movement known as New England Transcendentalism. His essays, books, and poems weave together two central themes over the course of his intellectual career: nature and the conduct of life. The continuing importance of these two themes is well illustrated by the fact that the last two essays Thoreau published during his lifetime were "The Last Days of John Brown" and "The Succession of Forest Trees" (both in 1860). In his moral and political work Thoreau aligned himself with the post-Socratic schools of Greek philosophy--in particular, the Cynics and Stoics--that used philosophy as a means of addressing ordinary human experience. His naturalistic writing integrated straightforward observation and cataloguing with Transcendentalist interpretations of nature and the wilderness. In many of his works Thoreau brought these interpretations of nature to bear on...