‘In the Blessed Trinity one Divine Nature subsists in three divine Hypostases (or Persons), who possess a real and identical nature in common; whereas in Christ two distinct and complete natures, one divine, the other human, subsist in one Hypostasis, i. e., the Divine Person of the Logos.
Or, to put it somewhat differently, the Blessed Trinity forms a real Trinity of Persons in an absolute Unity of Nature, whereas in Christ there is a duality of Natures in an absolute Unity of Person.
This twofold element in the constitution of the Godman is clearly stated in the ‘Athanasian Creed’
“For the right faith is that we believe and confess that our Lord Jesus Christ, the Son of God, is God and Man ; God, of the Substance of the Father, begotten before the worlds; and Man, of the substance of His mother, born in the world ; perfect God, and perfect Man : of a reasonable soul and human flesh subsisting; equal to the Father, as touching His Godhead: and inferior to the Father, as touching His Manhood. Who although He be God and Man: yet He is not two, but one Christ; one; not by conversion of the Godhead into flesh: but by taking of the Manhood into God; one altogether; not by confusion of substance : but by unity of Person.”
‘CHRISTOLOGY’ A DOGMATIC TREATISE ON THE INCARNATION’
by THE REVEREND JOSEPH POHLE, PH.D., D.D.1916