Few doctrines of the Catholic Church are as misunderstood as the two dogmas of the Immaculate Conception and the Incarnation. Simply put, the Immaculate Conception has to do with Mary and the Incarnation with Jesus. The Immaculate Conception is about Mary’s conception. It means that from the moment Mary was conceived, she was free from Original Sin. The Incarnation is about Jesus’ conception. It means ‘made flesh’, so meaning that Jesus was made flesh and because he is the second person in the Trinity, God was made flesh.
Many people, including many Catholics, think that the Immaculate Conception refers to the conception of Christ through the action of the Holy Spirit in the womb of the Blessed Virgin Mary. Actually, the Immaculate Conception refers to the condition that the Blessed Virgin Mary was free from Original Sin from the very moment of her conception. At the moment that her soul was joined to her body, God – in view of the merits of Christ – filled her soul with sanctifying grace. Whereas men receive sanctifying grace only at Baptism, and whereas John the Baptist received it at the Visitation, Mary, on the other hand, received grace at the first moment of her conception. In our case, the merits of Christ cleanse our soul from sin; in Mary’s case, the merits of Christ prevented sin from entering into and tainting Mary’s soul. In other words, Mary was preserved from original and from all sin.
The Incarnation refers to the uniting of the Son of God‘s divinity with a human body to become the God-man, Jesus Christ. Incarnation comes from a Latin term meaning “being made human flesh.” While this doctrine appears throughout the Bible in various forms, it’s in the gospel of John that it is fully developed: The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only Son, who came from the Father.