In the name of the Father and of the Son and of the Holy Spirit.

With the end of the Easter season, the Paschal Candle and the icon of the Resurrection have been returned to the Baptistery, and the Resurrection's place has been taken by Andrei Rublev’s famous 15th-century icon of the Trinity. Sometimes referred to as “The Old Testament Trinity,” its theme is the familiar story in Genesis of the patriarch Abraham’s three angelic visitors, a visit subsequently interpreted in Christian tradition as an image of the three persons of the Trinity. In it, the second Person of the Trinity - the Son, the Word, who reveals God to the world - is portrayed prominently in the center, pointing out into the world. The Father is seated to one side, looking lovingly at the Son, who in turn looks lovingly at the Father, while the bright-robed Holy Spirit is seated on the other side. The three Persons gaze at each other in mutual loving communication, into which we in turn are also meant to be drawn by the Son.

Well, you might say, that’s all very nice, but what of it? For so many (maybe most) of us, the Trinity has always seemed somewhat abstract – a doctrine duly believed in, of course, but not something otherwise given a lot of thought.

But I say this in spite of the obvious fact that we were all baptized in the name of the Father, and the Son, and the Holy Spirit. On that occasion, we – or our parents and godparents - all made a profession of faith in the Father, and the Son, and the Holy Spirit. Our sins have been forgiven in the sacrament of Penance, in the name of the Father, and of the Son, and of the Holy Spirit. Those of us who are married – including those couples being honored at this Mass today - have exchanged wedding rings in the name of the Father, and of the Son, and of the Holy Spirit. The principal prayers of the Mass are mostly addressed to the Father, through the Son, in the unity of the Holy Spirit. And we have all, over and over again, been blessed in the name of the Father, and of the Son, and of the Holy Spirit. In short, our entire religious lives, both individually and collectively as a Church community, have been defined, formed, shaped by this awesome Trinitarian mystery of who God is, that defines God’s ongoing relationship with us and ours with God.

In short, the doctrine of the Trinity is our uniquely Christian insight into who God is.  As human beings, created in God’s image and likeness, we all have a built-in, natural, longing for God. That God exists is something we can experience naturally.  But who God is - who God is in himself - is something we could never completely come to know on our own.  That had to be revealed to us by God himself. And God has done so, revealing who he is in himself – one God in three distinct Persons: Father, Son, and Holy Spirit.

We do not worship three gods, but one God – a unity of Persons in one divine nature or substance. Each of the three Persons, Father, Son, and Holy Spirit, is truly God, each distinctly God, but existing eternally in relationship to each other: the Father to the Son, the Son to the Father, the Holy Spirit to both. The very names Father, Son, Holy Spirit are relational names. By analogy, the titles “husband” and “wife” are names that are only understandable in terms of the relationships they signify.

On the one hand, the doctrine of the Trinity expresses our uniquely Christian insight into the ultimately incomprehensible inner life of God – where the Son is the image of the Father, the Father’s likeness and outward expression, who perfectly reflects his Father, while the Holy Spirit in turn expresses and reveals the mutual love of Father and Son. At the same time, the Trinity also expresses something fundamental about how God acts outside himself, how he acts toward us. Who God is in himself is how God acts; and thus how God acts in human history reveals who God ultimately is. Already in the Old Testament, God was revealing himself – as Moses testified in today’s 1st reading [Deuteronomy 4:32-34, 39-40] - as one who repeatedly reveals himself in how he acts toward us. 
                                          

It is, of course, the Son, consubstantial with the Father, who for our salvation came down from heaven, and who, seated at the right hand of the Father, has sent the Holy Spirit upon his Church, making her the Body of Christ and the Temple of the Holy Spirit. Led by the Holy Spirit – as Saint Paul told the Christians in Rome and through them tells us  [Romans 8:14-17]  - we become true sons and daughters of God the Father and joint heirs with Christ.

The Holy Spirit unites us with the Father in the Body of Christ, the Church. Through the sacraments, Christ continues to communicate the Holy Spirit to the members of his Church. Thus, at Mass the Church petitions the Father to send the Holy Spirit to sanctify the bread and wine that they may become the body and blood of Christ and that, filled with the same Holy Spirit, we who receive Christ’s body and blood may then be transformed into one body in Christ, participants in the mission of his Church.

That mission is nothing less than to make disciples of all nations - in the name of the Father and of the Son and of the Holy Spirit  [Matthew 28:16-20].

Homily for Trinity Sunday, Immaculate Conception Church, Knoxville, TN, May 31, 2015.