The early Church in Northern Africa made significant contributions to keeping Christianity faithful to the teachings of the apostles. Cyril of Alexandria (c. 376 – 444 AD) played an instrumental role in developing and defending orthodox Christology through his involvement in the Council of Ephesus and his theological writings. He was central in the early church's debates, particularly opposing Nestorianism, which emphasized the disunion between Christ's human and divine natures.

Nestorianism challenged the existing understanding of the unity of Christ by proposing that Jesus Christ was a union of two persons—one divine and the other human. This was in contrast to the orthodox view that Jesus Christ was a single person who was both fully divine and fully human. As Catholics, we accept the orthodox view.

In traditional Christian theology, the unity of Christ's divine and human natures is crucial for the redemptive role of Jesus. If Nestorianism had prevailed, it could have altered the perceived efficacy of Christ's actions as not just a divine intervention but as a partnership between his divinity and humanity, leading to a more fragmented understanding of salvation.

The orthodox Christian view emphasizes a personal relationship with Jesus Christ, who is fully God and fully man. If Nestorianism had prevailed, believers might have seen Christ more as a mediator between God and humans rather than God himself in human form, creating a distance in the personal relationship between the believer and Christ.

If Nestorianism had prevailed, Christianity today would be vastly different. It would affect everything from doctrine and worship to personal and communal identity as Christians, reflecting a more complex relationship with the divine mediated through a figure seen as both divine and human in separate capacities rather than unified in one person.

Cyril vigorously opposed Nestorius' teachings as a serious threat to the unity of Christ's person and the orthodox understanding of the Incarnation. He passionately argued for the unity of Christ's divine and human natures in one person, re-emphasizing that the divine Logos had become incarnate as Jesus Christ.

Coming out of Northern Africa, Cyril of Alexandria’s efforts were crucial in shaping orthodox Christological doctrine, asserting the belief in the unity of Christ's person. His legacy is that of a staunch defender of traditional Christological doctrine in the face of substantial challenges.