What theological position did the Council of Ephesus reject?

The Council of Ephesus, convened in 431 AD, primarily addressed the theological controversies surrounding the nature of Christ and the relationship between Christ's divinity and humanity. One of the key positions it rejected was Nestorianism, which proposed a distinct separation between the two natures of Christ—divine and human—suggesting that they were joined only by moral agreement. Nestorianism emphasized a duality that undermined the idea of a unified person in Christ.

The Council affirmed that in the person of Jesus Christ, there is a true union of both natures without confusion, change, division, or separation. This understanding was crucial in defining the orthodox Christian view of the Incarnation—one person, Jesus Christ, fully divine and fully human.

The rejection of Nestorianism at the Council of Ephesus helped solidify the belief in the hypostatic union, which plays a significant role in the mainstream Christian theology regarding Christ. This theological position served to counteract the implications of an overly divided Christology that Nestorius proposed, thereby maintaining the integrity of the belief in a single, united Christ who could truly be both God and man.