Trinity Sunday, also known as the Solemnity of the Most Holy Trinity, is celebrated a week after Pentecost Sunday in honor of the most fundamental of Christian beliefs—belief in the Holy Trinity. We can never fully understand the mystery of the Trinity, but we can sum it up in the following formula: God is three Persons in one Nature. The three Persons of God—Father, Son, and Holy Spirit—are all equally God. They cannot be divided. As the above diagram shows, each person of the Holy Trinity is a separate person, having been identified as such in the Holy Bible, but each are also the One True God. It’s why we make the sign of the cross in the Name of the Father and the Son and the Holy Spirit, rather than the “names.” It’s a profound mystery that many other religions reject. It’s not something that is easily explainable, but it was revealed by Jesus Christ through His Divine Word, and the Holy Spirit has filled our hearts and minds to help us understand it. We reinforce our belief in the Holy Trinity each time we make the sign of the cross.
The origins of the celebration of Trinity Sunday go back to the Arian heresy of the fourth century, when Arius denied the divinity of Jesus Christ by denying that there are three Persons in God. To stress the doctrine of the Trinity, the Fathers of the Church composed prayers and hymns that were recited on Sundays as part of the Divine Office, the official prayer of the Church. Eventually, a special version of that office began to be celebrated on the Sunday after Pentecost, and the Church in England, at the request of St. Thomas à Becket (1118-1170), was granted permission to celebrate Trinity Sunday. The celebration of Trinity Sunday was made universal by Pope John XXII (1316-34).
For many centuries, the Athanasian Creed was recited at Mass on Trinity Sunday. While seldom read today, the creed can be read privately or recited with your family to revive this ancient tradition.
