  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 apart from their correlatives. At least conceptually, they say, relations always come in pairs. Thus, even if there is no real or extramental property in Socrates that accounts for his being thought about by Simmias, we must still conceive of this situation as if there were one and, as it were, project this property onto Socrates. Since such projections depend for their existence on the activity of the mind, medieval philosophers refer to them as beings of reason (entia rationis). And their suggestion is that we take these beings of reason to be the items corresponding to or signified by concepts such as ‘thought about’.