Today the Latin / Western Church commemorates St. Augustine of Hippo.
One great ecclesiastical historian around here has called him the grandfather of the Western Church. Jaroslav Pelikan said that the whole of catholic history was the church’s struggle to understand and implement the doctrines of St. Augustine, and BB Warfield famously wrote that the Reformation was the conflict between Augustine’s doctrine of grace, Augustine’s doctrine of the church.
He has great prooftexts still used today, and you might read a Lutheran who quotes his words: “We may not assent to the teaching even of the Catholic bishops, if at any time they are deceived into opinions contrary to the canonical Scriptures of God” and likewise you might hear a Roman Catholic cite him for the opinion that they would not believe the gospels unless they were moved by the authority of the church.
Historians have creditted the man with beginning the entire psychological Western enterprise of introspection.
It seems everyone is in agreement at least on this: Augustine is important.