The first full-scale interpretation of the life and work of the major American neuropsychologist Karl Lashley. This book sets Lashley’s research at the heart of two controversies that polarized the American life and human sciences in the first half of the twentieth century. These concerned the relationship between ‘mind’ and ‘brain’ and the relative roles of ‘nature’ and ‘nurture’ in shaping behavior and intelligence. The book explodes the myth of Lashley’s neuropsychology as a fact-driven, ‘pure’ science by arguing that a belief in the power of heredity and a nativist and deeply conservative racial ideology informed every aspect of his theory and practice.