A dyadic relation is a character whose being consists in the logical possibility of a definite fact concerning an ordered pair, or dyad, of subjects; the first of these being termed the relate, the second the correlate; and the relation is said to subsist between the relate and correlate when the fact in whose possibility its being consists actually has place between these objects. The relation, by itself, is, therefore, an ens rationis and mere logical possibility; but its subsistence is of the nature of a fact. [—]
The broadest division of dyadic relations is into those which can only subsist between two subjects of different categories of being (as between an existing individual and a quality) and those which can subsist between two subjects of the same category. A relation of the former kind may advantageously be termed a reference; a relation of the latter kind, a dyadic relation proper.