The philosophies of HENRY DAVID THOREAU (1817-1862)-hero to environmentalists and ecologists, profound thinker on humanity's happiness-have greatly influenced the American character, and his writings on human nature, materialism, and the natural world continue to be of profound import today. In this essay, first published in the Atlantic Monthly in 1862 and vital to any appreciation of the great man's work, Thoreau explores: . the joys and necessities of long afternoon walks . how spending time in untrammeled fields and woods soothes the spirit . how Nature guides us on our walks . the lure...