The development of neurology in the late 19th century inaugurated a historical moment when the brain came to be taken seriously not only as the organ of thought, but also as the lynchpin of a materialist ideology. God and consciousness, many believed, had been excised from the natural world. Yet a movement of self-proclaimed French “spiritualists,” including Henri Bergson, Alfred Fouillée, and Jean-Marie Guyau, told a different story. They demonstrated that theology and metaphysics were not simply compatible with but sustained neurology and physiological psychology. What was spirit (l’esprit)? And the intellectual movement that went by the name of spiritualism? This installment of the Neuroscience and History Series explores the persistence of spirit within the experimental, quantitative, and pathological methods that lie at the origins of the modern neurosciences.