Most religious holy days celebrate some grand event that God brought to pass. The feast of Trinity this Sunday is the only major holiday in the church year that honors a theological doctrine.
The escape of slaves from bondage, the birth of a savior, resurrection from the dead and other dramatic events are acts of God, according to scholars who use them to shape our understanding of God in theology. The concept of the Trinity stands alone without specific historical roots.
The word, Trinity, is not in the Bible, but most Christian scholars argue that Scripture implies a God who makes himself known to the faithful in three distinct persons as Father, Son and Holy Spirit.
It is that sense of a triune God that Christians embrace that brings much consternation to Judaism and Islam. They argue that the idea of three persons in one God, however nuanced, muddies monotheistic waters.
The late Episcopal Bishop Jim Pike joked that Islam might be a more attractive religion than Christianity because Islam offered the faithful three wives and one God while Christians were stuck with one wife and three Gods.
There is no such levity in Trinitarian theology. The doctrine became critically important in early church struggles against those who refused to acknowledge the divinity of Jesus the Son and the independent divine work of the Spirit.