This study integrates literary and biographical criticism with social and cultural theory to make a major advance in our understanding of the life of two of America's most luminous intellectual figures. The central premise is that to contextualize the novelist inevitably involves assessing his relationship with his elder brother, William, and the study reveals how the psychological and cultural components of the Henry/William relation reciprocally interact. Posnock provides a new way to think about the relation of the brothers to each other and to their larger cultural moment: the challenge and trauma of early twentieth-century modernity.