  The distinction between what actually serves to relate things (i.e., genuine relations) and what merely stands in some relation (i.e., the relata of some relation) is often used by medieval philosophers to explain the difference between the two definitions in Categories 7. Whereas the first or Platonic definition includes both relations and relata (under relational descriptions), the second or Aristotelian definition includes only relations. This understanding of the difference between the two definitions provides the basis for a common medieval distinction between relations merely according to speech (relationes secundum dici) and relations according to being or nature (relations secundum esse). As Aquinas says, in a well-known passage of his Summa Theologiae: