The Trinity is a mystery. (Popular translation: The Trinity is a complicated, inexplicable – and not particularly exciting or spiritually relevant – doctrine.)
The Trinity is indeed a mystery, but not in the sense of being a giant theological puzzle, but – according to the theological meaning of the word “mystery” – a reality so rich, bright, multifaceted, and all-encompassing that we can never fully take in.
There are many ways to begin to understand the Trinity. The starting point, I propose, is the historical life and ministry of Jesus of Nazareth.
The first thing we notice is Jesus’ intimate relationship with the God of the Old Testament, who was hitherto rather remote and distant. The term Jesus used to address this God was abba, a word which means something like “dear father.” The first disciples learned to call God “Father” from observing the intimate way in which Jesus prayed.
This intimacy with the Father is the reason Jesus came to be called “Son of God” by his followers. His life and ministry were seen as God’s human presence. The Gospel of John succinctly summarizes this truth: “The Word was made flesh. He lived among us, and we saw his glory” (1:14). This led the Council of Nicaea to proclaim in 325 that Jesus himself is God.
All in all, Jesus is relatively easy to understand. He was born, ministered, preached, suffered, died, and rose again. We have a record of his career and his words.
When it comes to understanding Jesus’ relationship to the Father, we can call to mind artistic portrayals of Jesus kneeling in prayer to the Father, as in Jesus’ agonizing supplications in the garden of Gethsemane.
Now, to the Holy Spirit. My rule about starting with Jesus when thinking about the Trinity applies also when it comes to understanding the third person of the Trinity, the Holy Spirit. For it is on the matter of the Spirit more than anything else that we get into a real Trinitarian muddle.
We might begin by asking why the early Christians did not settle for God the Father, and Jesus, the Son. That would have made everything relatively nice and neat. The answer is that the disciples experienced after the resurrection – and particularly at Pentecost – a dimension of God’s presence and activity that belonged to a uniquely different realm from that of the Father and the Son.
This other realm of experience was more mysterious – like air, breath, fire, energy, fragrance. It was mostly invisible and silent, yet powerful and thrilling.
We are told that on Easter day, Jesus appeared to the disciples, “breathed on them and said to them, ‘Receive the Holy Spirit’” (John 20:23). Bring to mind a picture of Jesus breathing his resurrected life upon his disciples and you begin to understand who the Holy Spirit is. In a certain sense, the Spirit took on the personality of Jesus.
My rule about starting with Jesus when thinking about the Trinity is equally important here. Always think of the Holy Spirit as the Spirit of Jesus. The Spirit is the great gift that comes to us from Jesus’ risen life. All the gifts of the Spirit are gifts of Jesus.
Needless to say, much more would have to be added even for a cursory theology of the Trinity. On Trinity Sunday, however, we should not think we are dealing with a set of dry and dull abstractions, but rather with the great wealth and richness of God’s tri-fold presence revealed and experienced through Jesus in the communal life of the Church.