It is the most radical idea ever proposed and it has forever changed the history of the world.
It is, namely, the belief we have received from our Jewish brothers and sisters that there is only one God. Whereas Greeks, Romans, Babylonians and Egyptians worshipped many gods, the people of Israel worshipped only one God who was the Creator and Lord of all. This one God was not a part of the universe like the pagan gods but stood apart from it not only bringing it into being but sustaining it in existence. Unlike the Romans who had a god who just ruled the sea and another god who just ruled the sun, the God of Israel was Lord of all, with power over all of nature. He was not created but has always existed from all eternity. With time, the truth of this belief became more evident and, whereas people abandoned the pagan religions of the Greeks and Romans, to this day the God of Israel is worshipped and adored.
Another radical idea was later revealed to the people of Israel - that this one God became man in Jesus Christ. To those who followed Him, it became evident that Jesus was more than a good man, a wise teacher or a powerful prophet. They witnessed His power over nature when He walked on the water and calmed the raging storm. He claimed the power to forgive sins and could even tell what people were thinking. He called God, “Father”, and said that “I and the Father are one.” Finally, His resurrection from the dead convinced them that He truly was the Son of God leading Saint Thomas to cry out, “My Lord and My God.” This belief that Jesus Christ is true God and true man has likewise changed the course of human history, so much so that we mark time by the date of His birth. All of history revolves around the revelation of God in Jesus Christ and it is moving to its ultimate fulfillment when He will come again in glory.
From these radical ideas that there is only one God and that He became man in Jesus Christ follows a third - that God the Father and God the Son dwell within our hearts through the Holy Spirit. In today’s second reading, Saint Paul tells us that “...the love of God has been poured out into our hearts through the Holy Spirit that has been given to us.” In His essence, God is love. The love that God the Father has for His only Son is the Holy Spirit who is equally God. He lives in the hearts of all believers teaching us to love. Along with the Father and the Son, He dwells in our souls making us holy. And according to the promise of Jesus in today’s gospel that “...the Spirit of Truth...will guide you to all truth”, He dwells in our minds enlightening us and steering us clear of error and helping us to understand the will of our Heavenly Father.
From early on, it became clear to Christians that the Father, the Son and the Holy Spirit were all God. Rooted in the faith of the people of Israel, Christians always understood that they were not three gods but one God. However, it took time until this belief could be fully spelled out. It was the early Christian writer Tertullian who first used the word “Trinity” to describe the one God in three persons. Because it is a mystery, it would take many centuries more to find the right words and images to bring this belief into focus. This faith in the one God who is Father, Son and Holy Spirit stands at the center of our Christian belief and practice.
The Catechism of the Catholic Church makes three important points which help us to clarify and understand what we mean when we profess a belief in one God who is three divine persons.
The first point (CCC 253) is that when we assert our belief in God the Father, God the Son and God the Holy Spirit, we are not saying that we believe in three gods. Rather, the Trinity is one God in three persons. The Catechism goes on to say, “The divine persons do not share the one divinity among themselves but each of them is God whole and entire.” That is to say, God the Father is not partially God but fully God. The same is true of the Son and the Holy Spirit. Each one is God, fully and totally.
The second point (CCC 254) is that, while each being fully God, the persons of the Trinity are distinct from each other. That is to say, while God the Father and God the Son are both God, God the Father is not God the Son and God the Son is not God the Father. They are not separate “modes” or “images” that the one God has used to reveal Himself but real, distinct and separate persons.
The third point (CCC 255) is that we best understand the persons of the Holy Trinity in terms of how they relate to each other. God the Father, God the Son and God the Holy Spirit dwell in a continual relationship of life-giving love. From all eternity, God the Father gives Himself to God the Son. God the Son receives this love from God the Father. And God the Holy Spirit in a sense is the “breathe” of love which they continually give to and receive from one another. It is this ongoing exchange of love, which some theologians have referred to as a dance, that makes up the life of the Trinity.
It is easy to get confused trying to put this mystery into words. However, it is the central mystery of our faith and it is important for us to understand it as best we can, though we can never fully grasp it. That is why the Church gives us this celebration every year - to grow deeper in our knowledge of the reality of this God of love. It is not a merely intellectual exercise but an invitation to praise God who is beyond anything we can hope for our imagine. Furthermore, it is an invitation to marvel at the great love of God who not only reveals Himself to us but who draws us into His very self. Through baptism and by the presence of the Holy Spirit within us, we are drawn into this dance which takes place in the Trinity. We are caught up in love of the God we do not see and that love pours out into merciful works to our brothers and sisters whom we do see. All this in the hope that one day we will see God as He is and live forever with Him in heaven.