  [1] Sometimes it is a mere being of reason on the part of both relata, namely, when the order or [relative] disposition cannot exist between things except in virtue of the apprehension of reason alone. For example, when we say that something is identical to itself. For in virtue of the fact that reason apprehends the one thing twice, it regards it as two; and in this way it apprehends a certain [relative] disposition of a thing to itself. And the same thing is true of all relations between being and non-being, which reason forms insofar as it apprehends a non-being as a certain relatum. Again, the same is true of all relations that follow upon the activity of reason, such as genus and species, and the like.