Thoreau’s life has little in the way of outward adventure, so it’s essential that any biographer should seek the contours of his inward journey. Walls is unafraid to discuss difficult things, such as the author’s repressed sexuality. Emerson glanced at this side of his younger friend obliquely, calling him “a bachelor of thought and nature”. In his eulogy at Thoreau’s funeral, in a deleted passage, Emerson imagined his acolyte as “one of the old monks in their ascetic religion”. Walls writes, in a nicely restrained way, that “in another life, he might have found his life’s partner with a man”. In nineteenth-century New England, that possibility barely existed, and Thoreau in any case preferred his own company to that of anyone else. “In his acute, unspeakable awareness of difference from those around him”, says Walls, “he crafted a self of fluid but carefully guarded sensuality and intense, thwarted romantic energies, and he poured those energies, with ever-increasing passions, into his devotional life as an artist and prophet”.