Theory is not a set of texts, it is a style of approach. It is to engage in the act of speculation: gestures of abstraction that re-imagine and dramatize the crises of living. This Element is a both a primer for understanding some of the more predominant strands of critical theory in the study of religion in late antiquity, and a history of speculative leaps in the field. It is a history of dilemmas that the field has tried to work out again and again - questions about subjectivity, the body, agency, violence, and power. This Element additionally presses us on the ethical stakes of our uses of theory, and asks how the field''s interests in theory help us understand what''s going on, half-spoken, in the disciplinary unconscious.