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 how people live or ought to live.
Thoreau’s importance as a philosophical writer was little appreciated during his lifetime, but his two most noted works, Walden; or, Life in the Woods (1854) and “Civil Disobedience” (1849), gradually developed a following and by the latter half of the twentieth century had become classic texts in American thought. Not only have these texts been used widely to address issues in political philosophy, moral theory, and, more recently, environmentalism, but they have also been of central importance to those who see philosophy as an engagement with ordinary experience and not as an abstract deductive exercise. In this vein, Thoreau’s work has been recognized as having foreshadowed central insights of later philosophical movements such as existentialism and pragmatism.
Toward the end of his life Thoreau’s naturalistic interests took a more scientific turn; he pursued a close examination of local fauna and kept detailed records of his observations. Nevertheless, he kept one eye on the moral and political developments of his time, often expressing his positions with rhetorical fire as in his “A Plea for Captain John Brown” (1860). He achieved an elegant integration of his naturalism and his moral interests in several late essays that were published posthumously, among them “Walking” and “Wild Apples” (both in 1862).