 Scholars of religion who have used a polythetic approach have typically worked with a “bounded” approach (that is, with a properties set that is fixed), but this is not actually the view for which Wittgenstein himself argues. Wittgenstein’s goal is to draw attention to the fact that the actual use of concepts is typically not bound: “the extension of the concept is not closed by a frontier” (Wittgenstein 1953, §67). We can call this an “open” polythetic approach. To grasp the open approach, consider a group of people who have a concept they apply to a certain range of instances. In time, a member of the group encounters something new that resembles the other instances enough in her eyes that she applies the concept to it. When the linguistic community adopts this novel application, the extension of the concept grows. If their use of the concept is “open”, however, then, as the group adds a new member to the category named by a concept, properties of that new member that had not been part of the earlier uses can be added to the properties set and thereby increase the range of legitimate applications of the concept in the future. We might say that a bounded polythetic approach produces concepts that are fuzzy, and an open polythetic approach produces concepts that are fuzzy and evolving. Timothy Williamson calls this “the dynamic quality of family resemblance concepts” (1994: 86). One could symbolize the shift of properties over time this way: