The Feast of Trinity Sunday was celebrated throughout the whole Catholic Church only quite late – in the 14th century. In earlier times every Sunday was dedicated to the Holy Trinity. This was evident in the frequent reference to the Father, Son and Spirit as one God in the prayers of the liturgy. No special feast was needed.
The prayers and the focus of the Feast are very theological. That is to say, they express the Church teaching about the Trinity rather than exploring the place that Father, Son and Spirit have in the life of Christians and of the Church.
The emphasis on teaching about the Trinity can be traced back to one of the greatest challenges to Christian faith that took place in the 4th century. Christians became divided by the way in which they thought of God. Previously they had all prayed to the Father and to Christ and had recognised the work of the Spirit in their Christian lives. At the same time, they had insisted that the Christian God is one, in contrast to the many Gods of the pagans. Few were concerned how these convictions fitted together. In the 4th century, however, there was fierce debate in which the foundations of faith were at stake.
The crisis began when some Christians questioned the relationship between Jesus, the Son of God, and God the Father. They asserted that Jesus was central to Christian faith and was the special ambassador of God, but was a lesser being than God the Father. This belief was eventually seen to threaten the heart of the Gospel, which saw that God was personally involved in Jesus’ life and death. Jesus was not just God’s messenger but God’s Son. He is Son of God in the deepest sense, and through him God’s stake in humanity is God’s own self. The conviction that the stories and actions of Jesus are actions of God underlies the Feast of the Trinity.
The Christians who believed that Jesus was lesser than the Father then forced their opponents to address another central question. If Jesus, the Son of God, the Father and the Spirit are all God, how can they be the One God to whom Abraham and Jesus prayed, and not two or three Gods. The Church called to resolve the disputes did not explain how God is three and one, but used the language of one God in three Persons to assert both that God is one being and that Father, Son and Spirit share fully in divinity. The prayers and sermons on the Feast of the Trinity make that point again and again. It is not an explanation but a way of speaking that respects the full mystery of God’s love for us.
Unless we know a little about the history behind the words we use to describe God as Trinity it is easy to dismiss the belief as concerned with divine mathematics. It really celebrates something much deeper: the depth of God’s involvement with us in the salvation that Jesus brought us. It insists that when Jesus spoke to us, God speaks, when Jesus dies on the cross, God dies in him, that when Jesus rises and ascends to God he takes us with him and that when the Spirit works within our lives and Church, God works within us.
The Feast of the Trinity says that our world is not God’s colony under colonial management but is God’s home. It is about the intimacy of God’s presence to us in our world and in the Church through Jesus.