For the existence of the Holy Trinity we must rely entirely on revelation in the New Testament and the oral tradition of the Church which was the foundation of the New Testament. Human reason does not reveal the Trinity. Some claim that the Holy Trinity is revealed in the Old Testament, but the evidence is not there. However there are “footprints” of the Trinity in the Old Testament. God is often called Father or calls himself the Father of Israel as a people or nation. At the same time, the Israelites as a nation or a people are called God’s son, as are the kings of Israel. The activity of God as Spirit is widespread in the Old Testament beginning with the first creation story in Genesis 1:2. But there seems to be no revelation of a distinction of “Persons” in the Old Testament.
Has the Church always celebrated the Holy Trinity? Probably, since the baptismal formula used in the Great Commission of the disciples at the end of the Gospel of Matthew must have been in circulation and in Christian usage before Matthew composed his Gospel in the eighties of the first Christian century. Has there always been a liturgical celebration of the Trinity as a feast or solemnity? Rome was very slow in allowing an introduction of such a feast day. Towards the end of the eleventh century, Pope Alexander II still refused to establish such a feast day. He was of the opinion that no special feast was necessary since the weekly Sunday Masses already honored the Trinity. To this day, the Tridentine Latin Mass of Pius V uses the Preface of the Most Holy Trinity on the Ordinary Sundays of the liturgical year. The monks of Cluny in France were celebrating a feast of the Holy Trinity by 1091. St. Thomas Becket, archbishop of Canterbury, an English martyr, died 1170, introduced into England a special feast to honor the Trinity. Pope John XXII in 1334, living in Avignon, France, extended the feast of the Holy Trinity to the universal Church.
There has been a centuries-long dispute between the teaching of the Church affirming three Persons yet one God and those who deny the Trinity but affirm the One God — Trinitarians versus Unitarians. Even during and after the Reformation of the sixteenth century, the Catholic Church and the various Protestant denominations at least agreed on belief in the Trinity. Both Catholic and Protestant authorities were ready to exterminate as dangerous heretics deniers of the Trinity.
Trinity versus Oneness is a great divide between Judaism and Christianity. The Jews affirm their creed of the One God from Deuteronomy 6:4-5. This brief Hebrew creed begins: “Hear, O Israel, the Lord our God is one Lord, and you shall love the Lord, your God with your whole heart, etc.” We accept this Hebrew creed, truly believing that there is only one God. But we also have to do justice to revelation in our New Testament, which speaks of God the Father, God the Son, and God the Holy Spirit. The struggle in the first four centuries of Christianity was long and bloody, until the creeds were hammered out through Church Fathers and Doctors, Councils, and individual theologians.
Not until our union with God in eternity will we understand. In 1 Corinthians 13, St. Paul describes the darkness of our faith in this life and its counterpart in the life to come, “Our knowledge is imperfect, but when the perfect comes, the imperfect will pass away. When I was a child, I spoke as a child. When I became a man, I gave up childish ways. For now we see in a mirror dimly, but then face to face. Now I know in part. Then I shall understand fully, just as God has fully understood me.” Perhaps it is good to recall a technical term some theologians use to describe the relationship to each other of the three Persons in One God. The term is a Greek word, Perichoresis. It means singing and dancing together. We hope ultimately to be pulled into that joyful experience — the eternal round dance.
The gospel selection for this feast, John 3:16-18, describes how this joyful union and activity can come about. It is love, God’s love for us, followed by faith in the Son. Thus John writes in John 3:16. “God so loved the world that he gave his only Son, so that everyone who believes in him, might not perish, but have eternal life.” This gospel reading does not really mention the Holy Trinity, only Father and Son. But the second reading of the day ends with another well known expression, “The grace of the Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit be with you all,” 2 Corinthians 13:13.
