The Feast of the Most Holy Trinity: God is one God, three Divine Persons

Today, we celebrate the Feast of the Most Holy Trinity. Our belief in the Trinity is expressed whenever the Celebrant Priest says to you, “May the Peace of the Risen Lord, Jesus Christ, the Love of God the Father and the Companionship of the Holy Spirit” be with you all and you respond, “And with your Spirit.” We acknowledge our Faith in the Trinity, when after the homily, we recite together, “I believe in one God, the Father almighty…”. In that diversity of several hundred people reciting in unity, “I believe…” is the presence of the Trinity in our community. One God, three divine persons. Unity and plurality. 
 
Our Faith come to us through the Apostolic Tradition and the Scriptures:
 
God reaches out to us
In the Torah, God spoke to the people of Israel and Moses:
 

 “Did anything so great ever happen before? Was it ever heard of? Did a people ever hear the voice of God speaking from the midst of fire, as you did, and live?” Dt. 6

 
God is relational; he reaches out to us. God has a voice and is a nurturer and guide. We are not just meaningless particles afloat in a sea of meaningless particles, like abandoned children. We have a home and a God.
 
Here, God is revealed as the God who seeks relationship. The concept of Father and Son are, by definition, relational. They do not exist independent of others. Pope Benedict made this point in his wonderful book, Introduction to Christianity:

"St. Augustine once enshrined this idea in the following formula: “He is not called Father with reference to himself but only in relation to the Son; seen by himself he is simply God.” Here the decisive point comes beautifully to light. “Father” is purely a concept of relationship. Only in being for the other is he Father; in his own being in himself he is simply God. Person is the pure relation of being related, nothing else. Relationship is not something extra added to the person, as it is with us; it only exists at all as relatedness." Ratzinger, Joseph Cardinal. Introduction To Christianity, 2nd Edition (Communio Books) (Kindle Locations 2170-2173). Ignatius Press. Kindle Edition.

Christians recognize that Father, Son and Holy Spirit are only persons in relation to each other. In their being, they are God.  The Trinity is one God, three divine persons in relation to each other and seeking relationship with all the Father Creator has made. 

We have a Father
St. Paul wrote to the Romans that our response to the universe and its origin was not slavery or fear before the impersonal forces of matter and history, but an “Abba” to an adopting parent. We are full heirs to the God who need not have made us our sought us out. That is why God is like an adoptive parent. He is not stuck with us, he chose us. For Jews, Moslems and Christians, God chooses his people. The mystery of God, revealed in Christ wants relationship with us because, in his very being, God is divine relationship, Father, Son and Holy Spirit. St. Paul in his letter to the Romans calls God Father, Spirit and Lord,

“that we are children of God and if children, then heirs,
heirs of God and joint heirs with Christ, if only we suffer with him
 so that we may also be glorified with him.” Rom. 8

 
God speaks through His Word, Jesus Christ
God is a personal and relational reality. As persons made in the ‘image and likeness’ of God, we are adopted into this interpersonal reality of God and called to share it with others. 
 

“Full authority has been given to me both in heaven and on earth. Go therefore, and make disciples of all nations. Baptize them in the name of the Father and of the Son and of the Holy Spirit. Teach them to carry out everything I have commanded you. And know that I am with you always, until the end of the world.” Mt. 28

 
These doxologies of Father, Son and Holy Spirit are found in the Gospel and throughout the early Church. Our Faith is expressed in the Apostles and Nicene Creed. 
 
The Creed and Baptism: Our identity as Christians
The earliest known Israelite Creed is the Shema, 

“Hear O Israel, the Lord our God, the Lord is One.” Dt. 6:4.

The Creed of Israel, the Shema, is built on the sovereignity of God. There is one God which means, nothing else can be God. The Incarnation of God  reveals that the Divine is one, in the sense that ‘one’ means God, inherently a mystery. Mathematics is not an appropriate language for God because God transcends human conceptions.

Our Creed emerged from our earliest baptismal formulas. The form of baptism is that which is used today, “Do you believe in God, the Father almighty?” Response: “I do believe.” We repeat that formula for the Son and the Spirit. The Trinitarian formula was used as a greeting by St. Paul.  “May the grace of our Lord Jesus Christ, the love of God, and the fellowship of the Spirit be with you all” 2 Cor. 13:13. It was used as we began Mass today. 

The Trinity: Unity and Plurality as the Image of God
Genesis tells us about the Creation of the Human Person. “So God created mankind in his own image, in the image of God he created them; male and female he created them.” Gen. 1:27. Humanity is created in God’s image and likeness. We are one species, many individuals; unity and diversity. In the Creed we profess a common belief that unifies us. At mass we stand, kneel, sit and pray together. Yet, we all have our own emotional and intellectual life. We all have our own relationship with God. We experience unity in our communion and diversity in our own interior life. We were not made for loneliness, but for belonging. We do not live in isolation from each other, but are responsible for each other and too each other. Our lives are not our own, but are a gift to each of us. These are not contradictions, but are the experiences of the Divine Trinitarian life in our own human experience.