This paper is a comparison and contrast of approaches to many-valued mathematics offered by Fuzzy Set theory and topos theory. It gives a survey of the categorical foundations of Fuzzy Set theory and related topoi. Topoi are not a basis for Fuzzy Set theory but they do suggest appropriate directions to go and questions to ask for a synthesis which does provide a foundation. One possible structure which has a topos-like internal logic and the, rich variety of logical connectives used in fuzzy sets is included.