The general purpose of this dissertation is to explore casuistry--case-based reasoning--as a discredited, rehabilitated, and, most importantly, persistent form of moral reasoning. Casuistry offers a much needed corrective to principle-based approaches. I offer a defense of a "principle-modest" casuistry and explore the epistemology of casuistry, describing the prerequisite knowledge required for casuistry. I conclude by arguing that casuistry is best understood as a neo-premodernist approach to moral reasoning.