Filioque means and the Son . Western Christendom retains the phrase in the Nicene Creed, affirming that the Holy Spirit proceeds from the Father and the Son . Eastern Orthodoxy rejects the phrase, affirming instead that the Holy Spirit proceeds from the Father. Theologians on both sides admit that while the controversy may once have been important, it no longer carries much meaning for us. Even in the heat of the original dispute, it had more to do with a power struggle between Rome and Constantinople than with the true meaning of the Trinity.
Today is the Festival of the Holy Trinity, the festival of a very important church doctrine.
But I believe it is more than that. I believe it is a day on which the church celebrates God's full disclosure to us as Father, Son, and Holy Spirit. The church year began last Advent with the world God the Father created yearning for light and peace and joy. Then came the birth of God the Son, followed by his ministry, his passion and death, his resurrection and ascension. Finally came the outpouring of the Holy Spirit at Pentecost.