WHEN I was at school, Trinity Sunday usually fell during the exam season. The school hall, normally the location of the daily assembly, was taken over by neatly ordered desks and chairs. School prayers took place in the gym, where we sat on the floor. By the time I was preparing for O levels, as they then were, I had become a regular churchgoer, and I remember being struck by the Prayer Book readings for Trinity Sunday.

The Gospel described Nicodemus’s encounter with Jesus. For me, as a teenage Evangelical, this was a favourite passage, with its reference to being “born again”, though I did not, at that stage, pick up the baptismal imagery, assuming that the rebirth was an inward experience that came when you opened your heart to Jesus.

But what did intrigue me was the pairing of that reading with the one given for the epistle, from Revelation 4: “I looked, and, behold, a door was opened in heaven.” That open door became an important metaphor for me of the access that true faith enabled into the mystery of God. I also picked up, whether consciously or unconsciously, the echo of the prophet’s call in Isaiah 6. And then there was Bishop Reginald Heber’s famous “Holy, holy, holy”, which we always seemed to sing on the Monday after Trinity Sunday. Whenever I hear it now, I imagine I am back in the school gym, standing in my socks on its wooden floor, as we were not allowed to wear shoes in the gym.

Memory and association are powerful building blocks in the development of faith. When memories are benign, they can lead us to a more profound investment in the Christian mysteries.

Since studying early church history, I now know much more about the development of the doctrine of the Trinity, and the wranglings that went into the formation of the creeds and led to Christ’s being acclaimed as “of one substance with the Father”, and later to the affirmation of the divinity of the Holy Spirit.

I can point you to the relevant patristic texts by Athanasius, Basil of Caesarea, Gregory of Nazianzus, and Gregory of Nyssa. I can expound the meaning of ousia, hypostasis, and prosopon; and discuss possible misunderstandings when these terms are translated into Latin. I can explain why some Orthodox theologians find that Augustine’s exposition of the Trinity might not distinguish sufficiently between the three Persons, and why some Western Christians consider that the Orthodox might be closet subordinationists.

But, essentially, for me, Trinity Sunday is Nicodemus and Revelation, the invitation to be born again, the open door in heaven, and Bishop Heber’s hymn; scripture, liturgy, and the feel of the wooden floor of the gym under my socks. We remain of the earth even while we sing the praises of heaven. Holy, holy, holy, blessed Trinity!