How Does A Trinitarian Understanding of God Shape Ecclesiology? (1)
The doctrine of the Trinity has been decisive and divisive throughout Church history since the Councils of Nicaea and Constantinople of the patriarchal period. The major theological schism between the Western and Eastern Orthodox Church concerns chief elements of the doctrine of the Trinity. The way in which a church has believed and communicated the doctrine of God as Trinity has shaped the way in which the Church worships, fellowships, and communicates the gospel.
It may be helpful in developing how a Trinitarian understanding of God shapes an evangelical ecclesiology by first answering the question, why does a Trinitarian understanding of God shape an evangelical ecclesiology? First, because God as Trinity is how we know him to be the one true God. If we are to know God, then we must know him as three. While our knowledge of God will always be limited, full revelation of God will never reveal him as two or four, but only three. Part of knowing that we worship the God of Abraham is knowing him as three. Therefore, worshipping God as a Triune God is significant in worshipping God in spirit and truth. Second, God’s communication to his Church is Trinitarian. We are reconciled to the Father through the work of Christ (2 Cor. 5:18) and the Father seals us with his Spirit for the guarantee of our inheritance (Eph. 1:13-14). The Church’s communication with each person of the Godhead is Trinitarian. We know and commune boldly with the Father through Christ (Eph 3:12) and the Spirit stirs our affections for the Father so that we cry out “Abba! Father!” (Rom. 8:15) and creates categories of prayer to the Father that we do not have (Rom. 8:26). We know and communicate with Christ because of the witness of the Holy Spirit pointing to him (John 15:26) and the Father who bears witness to him (John 5:37). We know and commune with the Spirit because of the sending of Father and of the Son (John 16:1-7). Therefore, the reason why a Trinitarian view of God shapes an evangelical ecclesiology is because it is how the Church knows him and worships him in truth and it is how hold communion with him. These two aspects define much of evangelical ecclesiology.
Within the framework of knowing and communing with God, my effort, then, over the next few posts is to demonstrate how a Trinitarian understanding of God shapes the fellowship, worship, and communication of the gospel of the Church.
 Migliore, Daniel, Faith Seeking Understanding, 70.