Advancing a particular version of secularism, antebellum practices such as phrenology and spiritualism encouraged the conflation of moral agency with the directives of national security. In an attempt to situate such practices in relation to secular assumptions about politics in the mid-nineteenth century, this essay charts the deployment of occult ideas at Sing Sing State Penitentiary. Before their embrace of spiritualism in the early 1850s, both John Edmonds, the President of the Prison Association of New York, and Eliza Farnham, an advocate of phrenology, modified Sing Sing's evangelical approach to phrenology. Rather than continue to localize individual sin as the hinge of religious conversion, their methods focused increasingly on the cultivation of that which was both within and beyond the criminal body—the dormant potentiality of citizenship. To attend to the ascendancy of metaphysics at Sing Sing, I argue, is to begin to unpack the power and scope of what may be called, with all its disturbing ironies, a religion born of secular modernity.