Which key concepts did the heresies of the 4th and 5th councils primarily address?

The correct choice focuses on Trinitarian and Christological beliefs, which were central concerns of the ecumenical councils during the 4th and 5th centuries. This period was marked by significant theological debates, particularly about the nature of God and the identity of Jesus Christ.

The 4th Council of Nicaea in 325 addressed the nature of the Son in relation to the Father, ultimately affirming the doctrine of the Trinity and asserting the consubstantiality of Jesus with the Father against Arianism, which claimed that Jesus was a created being and not fully divine.

The following councils, particularly the Council of Chalcedon in 451, further developed the understanding of Christ’s dual nature, proclaiming that Jesus is both fully divine and fully human in one person—a crucial Christological doctrine that countered various heresies that either undermined Christ's divinity or humanity.

These councils played a critical role in shaping orthodox Christian theology by clarifying key issues related to the nature of the Trinity and the person of Christ, solidifying the foundation for Christian belief that remains influential to this day.