What theological issue did the Council of Ephesus in 431 AD address?

The Council of Ephesus in 431 AD is primarily known for addressing the theological issue surrounding the nature of Christ and the title of Theotokos for Mary. This council was convened to confront the Nestorian controversy, which questioned whether Mary could rightly be called the "Mother of God" (Theotokos) due to the belief that she bore only the human nature of Jesus. The council affirmed the title of Theotokos for Mary, emphasizing that Jesus Christ is one person with two natures—divine and human—conjoined in a hypostatic union. This declaration firmly established the doctrine of the Incarnation, affirming both the divinity and humanity of Christ, and ensuring that Mary is recognized as the Mother of God in the Christian faith.

The other options, while significant in their own right, were not the primary focus of the Council of Ephesus. The authenticity of the Old Testament pertains to biblical canon issues which were addressed in various historical contexts, but not uniquely at this council. The validity of apostolic succession, which deals with the continuity of the church’s leadership and authority, is another critical theological matter but also not a central issue at Ephesus. Finally, the relationship between faith and works touches on