Speaking of the Trinity, the Catechism of the Catholic Church  (no. 234) states that “the mystery of the  Most Holy Trinity is the central mystery of Christian faith and life. It is the mystery of God in himself. It is, therefore, the source of all the other mysteries of faith; it is the light that illumines them.”

It seems that the insistence on associating the concept of “mystery” with the Trinity corresponds to that “mysterious” halo with which Christians usually “cover” the thought about the Trinity, encompassing it in a series of truths of which, beyond repeating “mysterious” formulas, little can be known and even less can be lived.

This is because the Trinity is often thought of in terms of fundamentally philosophical concepts, such as “substance,” “nature,” or even “person,” which seem like abstractions far removed from everyday life. However, the Church has not professed faith in the Trinity based on philosophical reasoning, but rather based on divine revelation, which has taken place through actions and words (cf. Dei Verbum 2).

The action that most clearly revealed that God is a Trinity of persons has been the creation of humanity in his image, made up of men and women who are extremely different and, at the same time, profoundly called to live in communion and for communion. The convocation, in the midst of this immense humanity, of a people, Israel, who felt themselves children of the one God (cf. Hos 11:1-9), is a great step toward making unity in multiplicity present in the world.

But the definitive action that demonstrated God’s Trinitarian nature was the birth of the Church, the Body of Christ. Contemplating in awe the mystery of love among those who knew they were loved by Christ, the Church came to know the mystery of love between the Father, the Son, and the Holy Spirit. One is the Lover.

One is the Beloved. Likewise, one is Love. The gift of the Holy Spirit, the Love between the Father and the Son, constituted one people among all the peoples of the earth. And it is this experience of being loved without being homologized, and of loving the other without needing to “domesticate” them, that led Christians to intuit that this is what God was like: One and Triune.

The Gospels have left us numerous testimonies of all the times Jesus spoke of his union with the Father, and of the sending of the Spirit so that “they may all be one” (Jn 17:20-26), “so that the world may believe.”

Christians are baptized “in the name of the Father, and of the Son, and of the Holy Spirit,” and we are sent to baptize all peoples. But the fulfillment of this mission is not simply to make many people familiar with the Trinitarian formulas, but, fundamentally, to transmit the Trinitarian Life to them through a fraternal love like that which Christ has for us.

For this reason, the wounds to ecclesial unity have been and continue to be especially serious, and constitute one of the greatest difficulties for evangelization, because evangelizing is communicating the life of God, and God is Communion. It is difficult for anyone who peacefully coexists with offenses among brothers and sisters to speak of God-Communion.

To confess faith in the Trinity is not to repeat mysterious formulas, but to live gratefully in God’s love for us. To confess faith in the Trinity is to be amazed by the miracle that is the Church and, especially, by the power Christ has given her to forgive sins. To confess faith in the Trinity is to look to Christ and be willing to give one’s life to contribute to making all people one in Christ.