What is Trinity Sunday?

It is the day on which the church proclaims the doctrine of the Trinity, one God in three persons: Father, Son and Holy Spirit. It is appropriate to celebrate this soon after the Feast of Pentecost when the Holy Spirit appeared to his disciples.

During the early middle ages, and most intensely in the 4th century, there was much debate amongst Christians about the precise relationship between God the Father and the Son. Was the Son created by the Father at a particular point in time? The Arians (followers of Arius) believed that he was, and that he was therefore subservient to God, and by definition, finite. Those who upheld the notion that Christ was co-eternal and con-substantial (i.e. of the same nature) with the Father were led by Athanasius. It was the latter belief which was affirmed by the church as representing the implications of the New Testament.

Although the doctrine of the Trinity is not explicit in the New Testament, there are a number of places where such a doctrine is implied. The two most well-known of these are perhaps what is sometimes called ‘the Great Commission’, in which Jesus tells his disciples: ‘Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit’ (Matthew 28:19) and Paul the Apostle’s blessing: ‘The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all’ (2 Corinthians 13:14).

Ignatius of Antioch provides early support for the doctrine of the Trinity around the year 110, exhorting obedience to ‘Christ, and to the Father, and to the Spirit’. The first recorded use of the word ‘Trinity’ was by Theophilus of Antioch writing later in the 2nd century.

Thomas Becket (1118–70) was consecrated Archbishop of Canterbury on the Sunday after Pentecost, and his first act was to proclaim that the day should become a festival in honour of the Holy Trinity. This observance spread from Canterbury throughout the whole of western Christendom, with the effect that Pope John XXII (1316–1334) ordered that the feast be celebrated by the whole Church on the first Sunday after Pentecost.

An ancient Celtic prayer of praise from St Patrick’s Breastplate’:

I bind unto myself the Name,

The strong Name of the Trinity;

By invocation of the same.

The Three in One, and One in Three,

Of Whom all nature hath creation,

Eternal Father, Spirit, Word:

Praise to the Lord of my salvation,

Salvation is of Christ the Lord. Amen.