Western psychiatry emerged as a medical specialty caring for the mentally ill over the course of the late 18th and early 19th centuries. This emergence was a contingent process, dependent on the co-occurrence of three historical developments that together shaped the young discipline. The first was the rise of the mind as an entity with numerous active faculties in the conceptual space between the body and the Christian soul. Only by the latter half of the 18th century was it common to conceptualize conditions like mania or melancholy as illnesses. The second advance critical to psychiatry’s proto-specialty status, with its increasing focus on a mechanistic understanding of disease, was the rejection of humoral theories of insanity in favor of the brain and nerves as the seat of madness. The third development was the rise of the asylum. Only in dedicated institutions could mad-doctors be exposed to large numbers of the insane, permitting the development of a specialized clinical vocabulary grounded in faculties of mind, which led to new nosologic systems. The decline of humoral medicine, with its purges, bleeding, and emetics, and the urgent clinical need for care produced, in early asylums, the first novel treatment from the young specialty: moral therapy. We tell this story focusing mainly on the work of five philosophers and physicians: Descartes, Willis, Locke, Boerhaave, de Sauvages, and Cullen. Throughout its history, psychiatry has struggled with its sometimes disconjugate goals of understanding both mind and brain, with alternating efforts to expel one of these tasks from the profession. A historical perspective demonstrates that psychiatry is a profession inextricably linked to these two contrasting projects-and, indeed, jointly constituted by them.