What is the distinct and unique mark of Christian faith in the world of many religions today?  Muslims, Hindus, Buddhists, all believe in God.  But Christians have a different portrait of God. We proclaim our God when we say: In the Name of the Father, and of the Son and of the Holy Spirit.  We worship One God but we invoke three names.
One God in 3 Persons.  3 Persons but 1 God, not 3 gods.  Confusing at times and at times difficult.  That is why until today, many people do not believe in the Christian God, the Trinity.  Muslims refuse it; Mormons distort it; Iglesia members reject it.  Even intelligent people have difficulty. Once in a conversation with a young person he pressed on me the difficulty.  Mathematics has taught him that it is quite impossible that 3=1 and 1=3.
How do we understand this doctrine today?  I always say that God counts differently.  God counts not by the head by the heart.  The mathematics of God happens in the heart. Just remember that Jesus said in a parable that he was willing to leave behind 99 sheep for 1 lost sheep. Is 1 more important than 99?  Our God is really different.
It is not by counting that we understand God.  God becomes clearer to understand the moment we accept that he is love.  And love is never alone, but constantly looks for someone to offer its love.  In a normal family, we find a loving husband and a loving wife.  Their love produces children who will continue to love.  God is Trinity because God is love; he is a family of Father, Son and Holy Spirit.
But the family of God is not an enclosed family.  The love of God overflows to the world. We all become part of the life of God.  In the history of faith, we experience God as Father.  We experience God as the loving Son, our brother. We experience the Holy Spirit.  We are all part of the life of God, the Holy Trinity.
A wonderful example of this is the Blessed Virgin Mary.  In her, the Holy Trinity is so alive – daughter of the Father, Mother of the Son and Spouse of the Holy Spirit.
For us to understand the Trinity, we need to open our heart to God who is love and to allow this love to flow into our hearts.  Let us live and share this love to others.  We celebrate today a doctrine but not a mere idea.  It is an invitation to be part of the cycle of love that originates in God.