The belief in a Trinitarian God is uniquely Christian; no other major religion in the world professes that there are three Persons in one God. The concept of a Trinitarian God is not only unique, but also impossible to humanly explain. St. Augustine was quoted to say that if you deny the Trinity, you lose your soul, but if you try to explain it, you lose your mind. Although we cannot fully understand the mystery of the Holy Trinity, there are some things that have been revealed to us that are important for us to know and to understand, so that we can knowledgably live a Christian life.
When Jesus said that everything that the Father has belongs to the Son, and everything the Son has belongs to the Father (Jn 17:10), and that the Holy Spirit will take from what is of the Son and declare it to us (Jn 16:14), in a way, Jesus revealed the undivided unity of the Father, Son and Holy Spirit. The Catechism teaches us that the Trinity is One: the Father is that which the Son is, the Son is that which the Father is, and that the Father and the Son are that which the Holy Spirit is (CCC 253). The difficulty presented by this undivided unity is that although the three Persons are distinct from one another, they are one God. And even though each one is God whole and entire, they are not three separate gods.
So how is it that the Persons in the Holy Trinity are the same, and at the same time, not the same? The real distinction between the three Persons is found only in their relationships to each other – the first Person is the Father, the second Person is the Son, and the third Person is the Holy Spirit (CCC 255). God did not reveal himself to mankind as three Persons in one God in order to confuse or confound us. But on the contrary, it is in order for us to appreciate the extraordinary relationship of love among the three Persons. The unity of love within the Holy Trinity is so perfect that despite three Divine Persons, there can only be one God. The First Letter of St. John tells us that “God is love.” God’s very being is Love. By sending His only Son and the Spirit of Love in the fullness of time, God has revealed his innermost secret: God himself is an eternal exchange of love: Father, Son and Holy Spirit; and God has destined us to share in that love (CCC 221).
Our true understanding of the Holy Trinity does not depend so much on our theological knowledge, but on how we live our lives to reflect the love between the Father, the Son and the Holy Spirit. It is that extraordinary love of God – Father, Son and Holy Spirit – which has become a sacrifice that changed suffering from a curse to a love that transforms the whole world. The Cross is not just a symbol of the suffering Christ, it also represents the extraordinary love of the Holy Trinity for mankind. It is through the Cross of Christ that people have opened their hearts to the suffering of humanity.