  Although Aristotle discusses relations at various places in his work, his discussion in the Categories is the most important for understanding the development of medieval theories of relations. Part of the reason, as we have already indicated, is historical: until the twelfth century, the Categories is the medievals’ sole direct source for Aristotle’s views about relations. But part of the reason is more theoretical: in the Categories Aristotle develops a basic account of relations that is presupposed by his other discussions. Thus, even when some of these other discussions become available—discussions such as those in the Physics and Metaphysics—medieval philosophers continue to interpret them in light of their understanding of the Categories.