Ecumenical council

Reformed Christians accept four ecumenical councils.

• Council of Nicaea (325 AD): Affirmed the full divinity of Jesus Christ and condemned Arianism, establishing the Nicene Creed and the doctrine of the Trinity (the Son is of the same essence as the Father).
• Council of Constantinople (381 AD): Reaffirmed the Nicene Creed, affirming the full divinity of the Holy Spirit and clarifying the doctrine of the Trinity as equally one in essence and three in persons.
• Council of Ephesus (431 AD): Affirmed the title "Theotokos" (God-bearer) for Mary, defending the truth of Christ's full humanity and divinity against Nestorianism, which sought to separate the two natures of Christ.
• Council of Chalcedon (451 AD): Defined the doctrine of the hypostatic union, asserting that Jesus Christ is fully God and fully man, with two distinct natures united in one person, opposing both Monophysitism and Nestorianism.