This chapter investigates the boundaries and relations among medieval disciplines dealing with the natural world. Since medieval intellectuals themselves sought to organize the knowledge they inherited or produced about the natural world, their own views serve as a point of departure. The chapter surveys general notions about disciplines and their relations to one another as they were laid out before the twelfth century. It sketches some of the changes that rendered the older formulations obsolete. The chapter deals with the ways in which these changes were shaped by new conditions, especially the organization of learning within the university, between the thirteenth and fifteenth centuries. A highly influential work by Martianus Capella enumerated seven liberal arts, including three verbal disciplines such as grammar, rhetoric and logic, and four mathematical arts such as arithmetic, geometry, astronomy, and music. During the early Middle Ages, even the reiteration of fixed names and definitions could serve a variety of cultural, religious, and political functions.