The theological part of the work opens in c. 64 with
Hilary’s exposition of his own belief. He denies that there
is in God only one personality, as he denies that there is any
difference of substance. The Father is greater in that He is
Father, the Son is not less because He is Son. He asks his
readers to remember that if his words fall short, his meaning is
sound. This done, he passes to discuss the meaning of the word
ὀμοούσιον.
Three wrong meanings may be attributed to it. Firstly, it may be
understood to deny the personal distinctions in the Trinity.
Secondly, it may be thought to imply that the divine essence is capable
of division. Thirdly, it may be represented as implying that the
Father and the Son both equally partake of one prior substance. A
short expression like ὁμοούσιος must
therefore receive an exact explanation. A risk is attached to its
use, but there is no risk if we understand it to mean that the Father
is unbegotten and the Son derives His being from the Father, and is
like Him in power, and honour, and nature. The Son is subordinate
to the Father as to the Author of His being, yet it was not by a
robbery that He made Himself equal with God. He is not from
nothing. He is wholly God. He is not the Author of the
divine life, but the Image. He is no creature, but is God.
Not a second God, but one God with the Father through similarity of
essence. This is the ideal meaning of ὁμοούσιος, and in
this sense it is not an error to assert, but to deny, the
consubstantiality.