Mary's Motherhood Guarantees Jesus's Humanity

As Athanasius says:

...Our Saviour truly became man, and from this has followed the salvation of man as a whole. Our salvation is in no way fictitious, nor does it apply only to the body. The salvation of the whole man, that is, of soul and body, has really been achieved in the Word himself.

What was born of Mary was therefore human by nature, in accordance with the inspired Scriptures, and the body of the Lord was a true body: It was a true body because it was the same as ours. Mary, you see, is our sister, for we are all born from Adam.

The words of St John, the Word was made flesh, bear the same meaning, as we may see from a similar turn of phrase in St Paul: Christ was made a curse for our sake. Man’s body has acquired something great through its communion and union with the Word. From being mortal it has been made immortal; though it was a living body it has become a spiritual one; though it was made from the earth it has passed through the gates of heaven.

Even when the Word takes a body from Mary, the Trinity remains a Trinity, with neither increase nor decrease. It is for ever perfect. In the Trinity we acknowledge one Godhead, and thus one God, the Father of the Word, is proclaimed in the Church.