Trinity

As Christians developed their beliefs about Jesus, they explored how this was consistent with the God of the Old Testament – whom Jesus called Father – and the Holy Spirit given by Jesus to the early disciples (Acts 2.1-4, see John 20.22-3).

These beliefs are famously expressed in the Nicene Creed. The Creed speaks of God the Father, God the Son (Jesus), and God the Holy Spirit, three persons who are all one God. The Creed treads a middle path between saying there are three gods – Christians are monotheists (believe in one God) – and between saying it is one person who has three “roles” they switch between (modalism). Instead, Christians believe that God is three unique persons who are all equally divine as one God.

Christians often say that each person of the Trinity has particular responsibility for certain things (particularism). For example, the Father is particularly involved in creating the universe, the Son in saving humanity, and the Spirit in equipping the Church. Nevertheless, Christians believe that all three persons are fully involved in all that God is doing (perichoresis).

Sometimes Christians use other words to describe the persons of the Trinity. This is most common for “Father”, as this word can come with difficult connotations, with alternative words including “Creator”, “God” or even “Mother”. “Lord” often refers to Jesus, but in keeping with Old Testament usage can also be used for the Father.

Ultimately the Trinity is a bit of a mystery, which makes sense if God exists in dimensions beyond us! This doctrine is our best way of explaining how Christians encounter God – as with other “beliefs that”, they are part of the “belief in” a God whom people encounter in daily life.

Further resources

Books
Sarah Coakley, God Sexuality and the Self
Christine Helmer, The Trinity and Martin Luther
Anne Hunt, The Trinity: Insights from the Mystics
Arani Sen, Holy Spirit Radicals
Wm Paul Young, The Shack

Art
Although some Christians are hesitant to use art to express God (sometimes called iconoclasm), as this could risk us trying to make God in our own image, at its best Christian art helps us explore something of the nature of God, in a humble posture of knowing our words only go so far. 

Albrecht Dürer, Adoration of the Trinity
Jean Fouquet, The Trinity in all its Glory
Andrei Rublev, Trinity

As well as this art, Coakley’s book above contains several other instances. We also recommend Jane Williams’ Faces of Christ which contains art themed around Jesus’ life, death and resurrection. As an online introduction, we recommend Walking an Ancient Path.