"Because, on account of the incarnation of the Word of God for the working out of our salvation, that the man Christ Jesus might be the Mediator between God and men (1Ti 2:5), many things are so said in the sacred books as to signify, or even most expressly declare, the Father to be greater than the Son; men have erred through a want of careful examination or consideration of the whole tenor of the Scriptures, and have endeavored to transfer those things which are said of Jesus Christ according to the flesh, to that substance of His which was eternal before the incarnation, and is eternal. They say, for instance, that the Son is less than the Father, because it is written that the Lord Himself said, 'My Father is greater than I' (Jn 14:28).

"The truth shows that after the same sense the Son is less also than Himself; for how was He not made less also than Himself, who 'made Himself nothing, and took upon Him the form of a servant?' For He did not so take the form of a servant that He should lose the form of God, in which He was equal to the Father. If, then, the form of a servant was so taken that the form of God was not lost, since both in the form of a servant and in the form of God He Himself is the same only-begotten Son of God the Father, in the form of God equal to the Father, in the form of a servant the Mediator between God and men, the man Christ Jesus; is there anyone who cannot perceive that He Himself in the form of God is also greater than Himself, but yet likewise in the form of a servant less than Himself? And not, therefore, without cause the Scripture says both the one and the other, both that the Son is equal to the Father, and that the Father is greater than the Son. For there is no confusion when the former is understood as on account of the form of God, and the latter as on account of the form of a servant.

"In truth, this rule for clearing the question through all the sacred Scriptures is set forth in one chapter of an epistle of the Apostle Paul, where this distinction is commended to us plainly enough. For he says, 'Though he was in the form of God, did not count equality with God a thing to be grasped, but made himself nothing, taking the form of a servant, being born in the likeness of men.' (Phil 2:6-7). The Son of God, then, is equal to God the Father in nature, but less in 'likeness.' For in the form of a servant which He took He is less than the Father; but in the form of God, in which also He was before He took the form of a servant, He is equal to the Father. In the form of God He is the Word, through whom 'All things were made' (Jn 1:3); but in the form of a servant He was 'born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons' (Gal 4:4-5).

"In like manner, in the form of God He made man; in the form of a servant He was made man. For if the Father alone had made man without the Son, it would not have been written, 'Let us make man in our image, after our likeness' (Gn 1:26). Therefore, because the form of God took the form of a servant, both is God and both is man; but both God, on account of God who takes; and both man, on account of man who is taken. For neither by that taking is the one of them turned and changed into the other: the divinity is not changed into the creature, so as to cease to be divinity; nor the creature into divinity, so as to cease to be creature"

Augustine, On the Trinity, 1.7