My dissertation explores the religious history of intellectual disability and its treatment in the United States in the wake of the Second World War. While several scholars have marked this period as one in which what is now known as intellectual disability was “remade” in American public life (signaling the birth of a nascent disability rights movement), these studies have largely underplayed or neglected the role of religious practices and ideas in facilitating these changes. My project works to foreground those practices and ideas as part of a broader effort to reflect upon how diverse discourses have interacted in the making and maintenance of disability within a so-called “secular age.” Through an explication of popular and professional literatures, as well as select archives, I demonstrate the centrality of what was formerly known as “mental retardation” to many mid-century American Christians’ and Jews’ anthropological and moral imaginations. I illustrate how notions of cognitive difference helped diverse groups of social actors in this period articulate both what it meant to be human in the modern world and how persons within that world ought to be responsible for one another. By paying particular attention to the ways in which these forms of difference were (and were not) conveyed as matters religious, this project underscores the sorts of ethical claims that found purchase in the postwar United States and their roles in the assignment of cultural meanings to human diversity, agency, and vulnerability.