 This entry therefore provides a brief history of the how the semantic range of religion has grown and shifted over the years, and then considers two philosophical issues that arise for the contested concept, issues that are likely to arise for other abstract concepts used to sort cultural types (such as “literature”, “democracy”, or “culture” itself). First, the disparate variety of practices now said to fall within this category raises a question of whether one can understand this social taxon in terms of necessary and sufficient properties or whether instead one should instead treat it as a family resemblance concept. Here, the question is whether the concept religion can be said to have an essence. Second, the recognition that the concept has shifted its meanings, that it arose at a particular time and place but was unknown elsewhere, and that it has so often been used to denigrate certain cultures, raises the question whether the concept corresponds to any kind of entity in the world at all or whether, instead, it is simply a rhetorical device that should be retired. This entry therefore considers the rise of critical and skeptical analyses of the concept, including those that argue that the term refers to nothing.