The doctrine of the Trinity is considered a mystery because its meaning is made known to us only through God’s revelation. We could never have reasoned it out for ourselves; God – through the Holy Spirit – had to help us. As a mystery, God’s trinitarian reality will always be more than our human minds can ever fully comprehend.

The doctrine of the Trinity grew out of Christian’s experiences of God in revelation, redemption, and our response. In the New Testament both binitarian (meaning Father and Son alone; Romans 1:7, Ephesians 6:23) and trinitarian formulas are found (1 Peter 1:2; 2 Corinthians 13:14; Matthew 28:19).

Several passages in the New Testament begin to explore how the three Persons function and relate to each other. The three Persons are mentioned in 1 Thessalonians 1:1-9 (the first paragraph of the earliest New Testament writing from about 50 CE!), 1 Corinthians 12:4-6, Jesus’ farewell discourse at the Last Supper in John 14-16, and the baptismal formula of Matthew 28:19.

In the early Church, the trinitarian teaching appears in its baptismal creed, in its rule of faith, and in its doxologies. Yet, there was very little need to define or to explain it in strictly theological categories.

Finally, in the fourth century, so many difficulties had arisen that the former ways of explaining the doctrine were no longer satisfactory. A new expression, using philosophical and religious categories, was defined by the Councils of Nicaea (325 CE) and Constantinople (381 CE). The council members used a new philosophical terminology that was precise enough to make the clarifications were needed.

The real distinctions among the three Persons, the coequality of the three, and their co-eternity were expressed in the Nicene Creed. The Athanasian Creed (late fourth or early fifth century) further explained and clarified these important points.

The trinitarian doctrine affirms that there is only one God, expressed in three unique Persons who share the same divine reality. This doctrine has always challenged the attention and devotion of Christians.

Even our frustration to understand it invites us to enter more fully into this incomprehensible divine mystery. This same effort has often caused dissension during the history of the Church.

In the East, attention was focused on the differences that characterized the three divine Persons and their relationships. The differences were traced to their different origins. The Father is ungenerated (has no origin); the Son is generated from the Father; and the Holy Spirit proceeds from the Father through the Son.

In the West, attention was focused on the unity of the Persons. Saint Augustine and others believed that the Holy Spirit proceeded from both the Father and the Son.

This western doctrine was first included in the Nicene Creed when a local council added the Filioque clause in 589 CE. This clause takes it name from the Latin expression “and the Son” in the sentence “the Holy Spirit . . . proceeds from the Father and the Son.” The Filioque was eventually accepted at Rom around 1000 CE, where it was made official in 1214.

Rome’s unilateral actions was protested by the Eastern patriarchates. They thought it was important to stress the Father as a single source of divinity in the Godhead. The Eastern creeds expressed this single-source view by saying that the Spirit proceeded from the Father alone.

The Filioque clause has been both a cause and a sign of division between the Eastern and Western churches ever since. Theologians continue to study this issue in the hope of arriving at a theological explanation that will no longer be divisive to these Christian traditions.

The feast day of the Trinity developed in the 10th century. It was popularized in England by Thomas Becket who was consecrated archbishop of Canterbury on Trinity Sunday in 1162. The feast was made universal in the Western Church in the 14th century.

Living the Good News is an online lectionary-based curriculum published by Morehouse Education Resources. This essay is an example of the materials that are available on the LTGN Support Site for church use.