Psychiatrist Xavier de Oliveira's elision of spiritism with insanity is emblematic of early twentieth-century Brazilian psychiatry's alarmist preoccupation with spiritism as a public health threat. Between 1917 and 1928 he observed, in a sweeping hyperbole, that while alcohol and syphilis were the most common causes of psychosis among patients at the Psychiatric Clinic of the University of Rio de Janeiro, all the rest suffered from spiritism. This condition as a form and cause of psychopathology dominated the Brazilian psychiatric imagination during the early twentieth century as psychiatrists wrote medical and pseudo-medical treatises about it, dedicated entire medical journals to it, and made it a key topic of conversation at asylums and sanatoriums. As an organized profession confronted in Brazil with a popular, modern competitor—one with a radically different view of the self and of rationality—psychiatry was in a state of panic. Xavier de Oliveira and others placed both the doctrines of Kardecist spiritism and candomble, in their diversities of form and practice, under the conceptual umbrella of “spiritism” to refer to religious-philosophical systems of thought that postulated life after death through the viability of the spirit and the living's communication with spirits through human mediums. In the course of this chapter, I will use “spiritism” or “the spiritisms” to refer to the entire field of possession religions, including Kardecist spiritism and candomble as the two major branches within spiritism, while recognizing that there was, and remains, a diversity of belief structures between the two and within each.