It is at this point that the medieval notion of a relation of reason (relatio rationis) becomes relevant. Medieval philosophers often say that, even if there are relational situations involving only a single accident, nonetheless these situations must be conceived as if they involved a pair, one belonging to each of the related things (cf., e.g., Aquinas, De potentia q. 1, a. 1, ad 10). Like Boethius, the medievals accept the view that relations cannot be understood to exist by themselves or apa