The connection between mind and brain has been one of the most persistent problems in modern Western thought; even recent advances in neuroscience haven’t been able to explain it satisfactorily. Historian Larry Sommer McGrath’s Making Spirit Matter studies how a particularly productive and influential group of nineteenth- and early twentieth-century French thinkers attempted to solve this puzzle by showing the mutual dependence of spirit and matter. The scientific revolution taking place at this point in history across disciplines, from biology to psychology and neurology, located our mental powers in the brain and offered a radical reformulation of the meaning of society, spirit, and the self. Tracing connections among thinkers such as Henri Bergson, Alfred Fouillée, Jean-Marie Guyau, and others, McGrath plots alternative intellectual movements that revived themes of creativity, time, and experience by applying the very sciences that seemed to undermine metaphysics and religion. Making Spirit Matter lays out the long legacy of this moment in the history of ideas and how it might renew our understanding of the relationship between mind and brain today.