 What facts about the world or natural language or competent speakers could serve to fix sharp boundaries for vague words? According to Williamson (e.g., 1994b: 184), meaning supervenes on use; in other words, the locations of the sharp boundaries of a vague term are a function of speakers’ dispositions to use it as they do. (Insofar as the use of a vague term varies across time, its boundaries may be unstable.) Of course, we cannot know the totality of those dispositions, and we do not know the relevant function; and our ignorance of these factors blocks one path to knowledge of the locations of the term’s boundaries. 