Discussions of the relationship between science and religion typically assume that it is a relatively simple matter to establish clear boundaries for what counts as science and what counts as religion. Indeed, the idea that we can meaningfully discuss this relationship at all—whether it is conceived in positive or negative terms—relies to a large extent on our capacity to demarcate science and religion from other activities. In this lecture I suggest that the concepts 'religion' and 'science' are essentially modern inventions that often fail to capture the essence of the activities as they are conducted in practice. And while this is true of science and religion in the present, it is especially true of these enterprises in the past.