This article analyses the motives behind the conflicting positions taken by Victorian Roman Catholics over the issue of vivisection. Catholics defended or attacked vivisection for widely varying reasons; there were less two schools of thought than a mosaic of arguments from which to choose. While there was substantial agreement over basic theological principles, the application of those principles to the vivisection debate varied depending upon the writer’s social, political, and scientific attitudes, which in turn were affected by professional occupation. The debate included laypeople as well as clerics, with some of the former affirming a more liberal and less theologically rigorous approach to animal rights.