On the Solemnity of the Most Holy Trinity, the Church celebrates the central doctrine of faith that we profess as Christians, the oneness of the Holy Trinity. This doctrine of the faith is a profound mystery of faith that can only be known through Divine Revelation. Reason alone cannot lead us to an understanding of the inner mystery of God as a Trinity of Persons. So how can we know that God is a Trinity of Persons? We have received this truth from Jesus the Son who came to reveal to us the Father and who sent to us the gift of the Holy Spirit. “No one has ever seen God. The only Son, God, who is at the Father’s side, has revealed him.” (Jn 1,18) Jesus reveals this mystery to his disciples in the gospel of Matthew: “At that time Jesus said in reply, “I give praise to you, Father, Lord of heaven and earth, for although you have hidden these things from the wise and the learned you have revealed them to the childlike. Yes, Father, such has been your gracious will. All things have been handed over to me by my Father. No one know the Son except the Father, and no one knows the Father except the Son and anyone to whom the Son wishes to reveal him.” (Mt 12,25-27) The teaching of the Holy Trinity, One God in three Persons, comes to us from Jesus who is sent by the Father to reveal to us the inner life of God and to invite us into a share in the Divine Life.
Jesus first led the apostles to recognize gradually that he was the Son of God, sent by the Father, through his teachings and through his works. This is something that only faith can reveal to us as no philosophical system can lead us to this truth, as Jesus points out to Peter when he makes his profession of faith at Caesarea Philippi that Jesus is the Son of the Living God: “Blessed are you, Simon son of Jonah. For flesh and blood has not revealed this to you, but my heavenly Father.” (Mt 16,17) He goes on to reveal to the apostles that he and the Father are one and that to see him is to see the Father: “Have I been with you for so long a time and you still do not know me, Philip? Whoever has seen me has seen the Father. How can you say, ‘Show us the Father’? Do you not believe that I am in the Father and the Father is in me? The words that I speak to you I do not speak on my own. The Father who dwells in me is doing his works. Believe me that I am in the Father and the Father is in me, or else, believe because of the works themselves.” (Jn 14,9-11) One can come to know the interior life of the Holy Trinity, the “Immanent Trinity,” through the words, teachings, deeds and “works” that are accomplished in Jesus’ name. The visible “works” of the Trinity are the “Economic Trinity.” We can know “who God is” by “what he does.”
Jesus promises to send the Holy Spirit to the apostles after his ascension to lead them into the deeper Truths of Faith. “Jesus said to his disciples, “I have much more to tell you, but you cannot bear it now. But when he comes, the Spirit of truth, he will guide you to all truth. He will not speak on his own, but he will speak what he hears, and will declare to you the things that are coming.” (Jn 16,12f) He culminates his revelatory teaching with the baptismal commission to go out and make disciples of all people, “baptizing them in the name of the Father, and of the Son and of the Holy Spirit.”(Mt 28,19) That these three all share the one divine “name” and that they are joined by the “and” helps us to see the unity of Persons in the Trinity. We believe in One God as a unity of three distinct Persons.
The revelation of the intimate inner life of God teaches us not only about God, his divine will and mission, but it also teaches us about ourselves who are created in the Divine Image and Likeness. As God exists from eternity as a dynamic communion of love and shared life and intimacy, so are we to seek to live in communion with one another, loving one another and giving ourselves to one another in a shared life of love. Jesus prayed that we might realize this truth in our lives and ministry in his final prayer to the Father: “I pray not only for them, but also for those who will believe in me through their word, so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me. And I have given them the glory you gave me, so that they may be one, as we are one, I in them and you in me, that they may be brought to perfection as one, that the world may know that you sent me, and that you loved them even as you loved me.” (Jn 17,20-23) Let us live always in that love and draw our life from that deep ocean of love shared in the Most Holy Trinity.