y
virtual quantity is measured both in regard to being and in regard to
action: in regard to being, forasmuch as things of a more perfect
nature are of longer duration; and in regard to action, forasmuch as
things of a more perfect nature are more powerful to act. And so as
Augustine (Fulgentius, De Fide ad Petrum i) says: "We understand
equality to be in the Father, Son and Holy Ghost, inasmuch as no one
of them either precedes in eternity, or excels in greatness, or
surpasses in power."

Reply Obj. 2: Where we have equality in respect of virtual quantity,
equality includes likeness and something besides, because it excludes
excess. For whatever things have a common form may be said to be
alike, even if they do not participate in that form equally, just as
the air may be said to be like fire in heat; but they cannot be said
to be equal if one participates in the form more perfectly than
another. And because not only is the same nature in both Father and
Son, but also is it in both in perfect equality, therefore we say not
only that the Son is like to the Father, in order to exclude the
error of Eunomius, but also that He is equal to the Father to exclude
the error of Arius.

Reply Obj. 3: Equality and likeness in God may be designated in two
ways--namely, by nouns and by verbs. When designated by nouns,
equality in the divine persons is mutual, and so is likeness; for the
Son is equal and like to the Father, and conversely. This is because
the divine essence is not more the Father's than the Son's.
Wherefore, just as the Son has the greatness of the Father, and is
therefore equal to the Father, so the Father has the greatness of the
Son, and is therefore equal to the Son. But in reference to
creatures, Dionysius says (Div. Nom. ix): "Equality and likeness are
not mutual." For effects are said to be like their causes, inasmuch
as they have the form of their causes; but not conversely, for the
form is principally in the cause, and secondarily in the effect.

But verbs signify equality with movement. And although movement is not
in God, there is something that receives. Since, therefore, the Son
receives from the Father, this, namely, that He is equal to the
Father, and not conversely, for this reason we say that the Son is
equalled to the Father, but not conversely.

Reply Obj. 4: In the divine persons there is nothing for us to
consider but the essence which they have in common and the relations
in which they are