The problem with the York Mystery Plays was not that "God" was a woman; for it is always worth being reminded that God transcends all our human categories. The problem, or so it seemed, was the moment when the Virgin Mary was lifted high above the stage on a third golden throne to join God the Parent and God the Son. It looked as if she was being substituted for the Holy Ghost. Was this some over-subtle feminist ploy, or simply a misunderstanding?

Fortunately, the misunderstanding was mine. The York Cycle consists of nearly 50 plays, covering the Biblical story from Creation to the Last Judgement. The play performed in York nowadays is a selection from these plays, adapted and welded into a continuous whole. The scene that had misled me was simply the result of the Ascension and the Coronation of the Virgin being compressed to save time.

But I still think that the three golden thrones were a mistake. For in heaven there may be only one throne, or lots of thrones. There simply cannot be three.

"How many thrones are there in heaven?" Even to ask the question seems absurd. It evokes the ghostly shade of a medieval scholastic pondering the number of angels on a pinhead. But it is the job of theologians to notice the wider implications of questions that appear trivial. That is how they make disembodied ideas live. Perhaps it matters how many thrones are in heaven.

So first let me state my thesis boldly. In heaven, there is one throne, which is God's. This matters, because the Christian God is trinitarian, but is not three people. On the contrary, the doctrine of the Trinity holds that God is one. The number of thrones in heaven represents, imaginatively, the way that God may touch us in our ordinary lives.

At the end of the original York Cycle, the Son judges humankind as the representative of the Father. They are not two separate people, but two persons in one, united "in will and work both night and day". When the Father sends the Son to suffer on earth, this is not the cowardly act of a tyrant getting someone else to do his dirty work for him. For the work of the Son is the work of the Father. That is why it makes sense to say: "God so loved the world that he gave his only Son . . . that the world might be saved through him".

The Spirit is the symbol of that unity, flowing from the Father through the Son into the hearts of those who hear the Son's call. The York Cycle describes the Holy Ghost coming down on the disciples at Pentecost "our minds with mirth to mend". The joy that the Spirit brings is the joy of the presence of God. The work of the Trinity is one. That is why there is one throne.

But the life of the Spirit is given to many. That is why there may be many thrones, for all the other saints. Sometimes it seems as if the Church's hierarchy has been battling with charismatic outsiders for exclusive control of the Spirit. But the Spirit "blows where it wills", and can be claimed by neither priests nor prophets. The Spirit is at work in the daily lives of ordinary members of the Church.

The mystery plays were written and performed by and for working people. Each of the plays was the responsibility of a guild of craftsman; they were acted in the open air across the city, during the holiday of Corpus Christi. This year's production at York gave the plays back to the people: for once the cast was entirely amateur and local.

It was fitting, then, that the high points of the play should be its humblest moments: the innocent playfulness of Adam and Eve in paradise, the anguish of the gentle Abraham, called to sacrifice his beloved son, the knockabout humour of Noah's family, the characterisation of the Pharisees as "bishops". Here the plays breathed with their original life: the Word of God was being communicated through the people, by the people, for the people. The Holy Ghost descended in Jerusalem upon fishermen to enable them to teach and preach; and in York upon tanners and tailors; and now upon solicitors and shop assistants.

There is, so to speak, a single throne in heaven: for the work of the triune God is one. But if there are also many, lesser, thrones, it is because the Spirit has filled the people of God, as they live their ordinary lives, and infused them too with the life of the Blessed Trinity.