“I am alarmed,” wrote Henry David Thoreau in “Walking,” his 1862 essay, “when it happens that I have walked a mile into the woods bodily, without getting there in spirit.” The point of his saunter had been to “forget all my morning occupations, and my obligations to society.” Alas: “It sometimes happens I cannot easily shake off the village.” His thoughts were elsewhere. With a gentle lashing of self-reproach, he asks: “What business have I in the woods, if I am thinking of something out of the woods?”