What is the central doctrine of the Catholic Faith? Some might say that it is the doctrine of the Eucharist, or of the sacraments in general; others might answer that it is the doctrine of Original Sin, or more broadly of Creation-Fall-Salvation-Sanctification. It might be argued that our central doctrine is the revelation of Christ as true God and true man, or that He established a Church through which God would continue to teach us and speak to us until the world's end. These are all very important doctrines, but none of them is ultimately the central doctrine of the Catholic Faith. Rather, the core doctrine of our faith—the central tenet in which all other doctrines are rooted—is the doctrine of the Trinity. The Catechism of the Catholic Church (CCC) tells us that
“From the beginning, the revealed truth of the Holy Trinity has been at the very root of the Church's living faith, principally by means of Baptism. It finds its expression in the rule of baptismal faith, formulated in the preaching, catechesis, and prayer of the Church” (CCC 249).It is therefore worth asking what is meant by the doctrine of the Trinity. The best summary of the doctrine is to say that there are three distinct persons united in one divine nature, that is, that there is one God in three persons. Oddly enough, though we do find references to all Three Persons of the Trinity in the Bible (see, for example, 1 Corinthians 13:13, Galatians 4:6 or John 14-17), the doctrine itself is not formulated in the Bible but rather through Tradition and through the teaching authority of the early Church.
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