Surely a division now called the "Great Schism" should command our attention, but it is vital that we do not impute similar significance to all modern disagreements in the church.
Adiaphora is a theological term that means "indifference." It typically refers to practices that are neither commanded nor forbidden by God in Scripture.
The celebration of Trinity Sunday–the only church festival specifically dedicated to a doctrine–reminds us of the necessity of confessing that the one God exists in three persons, Father, Son, and Holy Spirit.