as,
"Behold I go to the Gentiles" (65:1), a gloss adds, "The Son speaks
Who said to Moses, I am Who am." These appear to belong to the Son,
and are not appropriated. For "truth," according to Augustine (De
Vera Relig. 36), "is the supreme similitude of the principle without
any dissimilitude." So it seems that it properly belongs to the Son,
Who has a principle. Also the "book of life" seems proper to the Son,
as signifying "a thing from another"; for every book is written by
someone. This also, "Who is," appears to be proper to the Son;
because if when it was said to Moses, "I am Who am," the Trinity
spoke, then Moses could have said, "He Who is Father, Son, and Holy
Ghost, and the Holy Ghost sent me to you," so also he could have said
further, "He Who is the Father, and the Son, and the Holy Ghost sent
me to you," pointing out a certain person. This, however, is false;
because no person is Father, Son and Holy Ghost. Therefore it cannot
be common to the Trinity, but is proper to the Son.

_I answer that,_ Our intellect, which is led to the knowledge of God
from creatures, must consider God according to the mode derived from
creatures. In considering any creature four points present themselves
to us in due order. Firstly, the thing itself taken absolutely is
considered as a being. Secondly, it is considered as one. Thirdly, its
intrinsic power of operation and causality is considered. The fourth
point of consideration embraces its relation to its effects. Hence
this fourfold consideration comes to our mind in reference to God.

According to the first point of consideration, whereby we consider
God absolutely in His being, the appropriation mentioned by Hilary
applies, according to which "eternity" is appropriated to the Father,
species to the Son, "use" to the Holy Ghost. For "eternity" as
meaning a "being" without a principle, has a likeness to the property
of the Father, Who is "a principle without a principle." Species or
beauty has a likeness to the property of the Son. For beauty includes
three conditions, "integrity" or "perfection," since those things
which are impaired are by the very fact ugly; due "proportion" or
"harmony"; and lastly, "brightness" or "clarity," whence things are
called beautiful which have a bright color.

The first of these has a likeness to the property of the Son, inasmuch
as He as Son has in Himself truly and perfectly the nature of the
Father. To insinuate this, Augustine says in his