Today is possibly my favourite moment in the (Western) liturgical year — Trinity Sunday.
What I love so much about Trinity is the way it makes us pause and look back over the key moments leading up to it — Christmas, Good Friday, Easter, Ascension and Pentecost — and put together the whole picture. In the dramatic events of Jesus’ life, death, resurrection, ascension and subsequent sending of the Spirit, we have to do with God … in person! At the climax of salvation history God decisively manifests himself as Father, Son and Holy Spirit.
More than that, in the gracious overflow of his love — which takes the concrete form of the cross and resurrection of the Messiah — God draws us into profound union with him, sharing with us his own life and fellowship. Such is the result of trusting in the good news according to 1 John 1.1-3 (for example):
This is why I consider myself acatholic Christian. Not that I’m aligned with the Roman church particularly. But that I rejoice in the truth that’s the distinctive mark of historic, creedal, catholic Christianity: the gift of fellowship with Father, Son and Holy Spirit, which constitutes the church as the community of believers.
O’Donovan (On The Thirty Nine Articles, p 93) has a good word on this:
There has to be a bridge between evangelical theology and ecclesiastical theory; that is, there has to be a theology of the church as such, which in turn will be the basis for the administrative tasks of church organization. That theology must not detract from the place of Christ at the centre of the gospel message. Yet to speak of the work of Christ it is necessary to speak of its result: a restored humanity, with Christ as its head, living in the light of God’s presence. The catholic church is as much of that restored humanity as we have been given to see, a community in which the Holy Spirit dwells, expectantly anticipating the revealing of God’s kingdom.