Within the Catholic family, the two Sundays that follow the great Feast of Pentecost celebrate two solemnities of the Lord. The second of those will be this coming Sunday as we celebrate the Feast of the Most Holy Body and Blood of Christ, or Corpus Christi. In many parts of the world this feast is celebrated this Thursday, but in the U.S. it is moved to Sunday. The other feast was that of the Most Holy Trinity yesterday - celebrating the Oneness of the Godhead as it is expressed in Three Distinct Persons ... Father and Son and Holy Spirit.
We are a Trinitarian people. All of our belief in the One God is summed up in that revelation of God to us. We were baptized in the Name of the Trinity. We begin and end every prayer with that expression of faith. Our worship is rooted in that belief, our Faith is expressed in Trinitarian Creeds. We are children of the heavenly Father, sisters and brothers with the Lord Jesus, and sharers in the life giving Spirit of God.
Before the Saturday evening Mass, I mentioned to a few people that my homily may be brief. I said that, in fact, it could be as simple as stating the obvious "In the name of the Father, and of the Son, and of the Holy Spirit." But I assured them that it probably would be a little longer. One of the ladies then said that I could add an "Amen" to the end of the sermon, making it that much longer. However, it was longer than either of those expressions of Trinity.
The uniqueness of believing in only one God flows from a revelation by a higher power than ourselves, a Supreme Being, revealed to the descendants of Abraham ... first to the Hebrew people, then to the followers of Jesus in the new covenant, and even to the followers of Mohamed. The manifestation of that one God is seen in the role of life-giver, creator God, Covenant maker, Father ... in the person of Jesus, the Christ (the Anointed One) whom the Father sent to us to be His Word of life, to redeem what was lost by sin, to show us the way to the Father, to help us understand that we can now call God "Abba", Father, daddy, and to restore us through his death and resurrection ... and to be sustained, empowered, strengthened, renewed, sent forth with and in their Spirit, the Paraclete, the Advocate, the Sanctifier. This is who we are. This is who God is in relationship to us. This is our Faith, and we proud to profess it in Christ Jesus, our Lord.