Before God created, he knew what he would reveal and how he would save us. So, he included in creation all the realities he would use to make himself and his plan for us known, and to carry out that plan. Among those realities are sex and the interpersonal relationships that presuppose sex. Thus, God created fathers and sons so that he could reveal himself as Father and Son, and call us to be children in the divine family; he created marriage, so that he could faithfully love Israel as his unfaithful wife, make the Church the Lord Jesus’ spotless bride, and promise an unending heavenly marriage feast. He made both motherhood and virginity possible, so that the incarnate Word could be both the Son of God and the son of Mary, whose virginity points to Jesus’ divine origin and personhood, and whose motherhood manifests his humanity.

The Incarnation, considered as the coming to be of the created humanity assumed by the Word, neither began nor ended at the Annunciation. Part of any human individual's make up and identity is having ancestors, living within a tradition, belonging to a community, and sharing its culture. Thus, the whole history of Israel is necessary for Jesus to come to be as the man he is and to live the life he lives. Mary in particular contributes to Jesus’ make up and very identity. To regard her as simply and absolutely other than the Lord Jesus is either to deny the Incarnation or to suppose that a real human individual can be only contingently related to his or her parents—to suppose that each of us could have had other parents while remaining the same individual.