Certain propositions in the logic of relation deserve to be mentioned
if u ,v be any two classes ,
there is a relation R the assertion of which between any two terms x and y is equivalent to the assertion that x belongs to u and y to v
if u be any class which is not null , there pairs of terms
there is a relation which all its terms have to it, and which holds for no other pairs of terms
if R be any relation, and u any class contained in the class of referents with respect to R , there is a relation which has u for the class of its referents, and is equivalent to R throughout that class;