Most Holy Trinity

Most Holy Trinity
By Abbot Father Michael Cuozzo+, OFE
The divine Trinity takes up his abode in us on the day of our Baptism: “I baptize you in the name of the Father, and of the Son, and of the Holy Spirit”. Every time we sign ourselves with the sign of the Cross we remember God’s name in which we were baptized. With regard to the sign of the Cross a theologian, Romano Guardini, remarked: “We do it before praying so that… we may put ourselves spiritually in order; focus thoughts, heart and will on God; after praying, so that what God has given us may remain within us…. It embraces the whole being, body and soul… and everything is consecrated in the name of the Triune God” (Lo spirito della liturgia. I santi segni, Brescia, 2000, pp. 125-126).
What is the dogma of the Holy Trinity?
The Trinity is One. We do not confess three Gods, but one God in three persons, the “consubstantial Trinity”. The divine persons do not share the one divinity among themselves but each of them is God whole and entire: “The Father is that which the Son is, the Son that which the Father is, the Father and the Son that which the Holy Spirit is, i.e. by nature one God.” In the words of the Fourth Lateran Council (1215), “Each of the persons is that supreme reality, viz., the divine substance, essence or nature.” (Catechism of the Catholic Church, 253)
The divine persons are really distinct from one another. “God is one but not solitary.” “Father”, “Son”, “Holy Spirit” are not simply names designating modalities of the divine being, for they are really distinct from one another: “He is not the Father who is the Son, nor is the Son he who is the Father, nor is the Holy Spirit he who is the Father or the Son.” They are distinct from one another in their relations of origin: “It is the Father who generates, the Son who is begotten, and the Holy Spirit who proceeds.” The divine Unity is Triune. (Catechism of the Catholic Church, 254)
The divine persons are relative to one another. Because it does not divide the divine unity, the real distinction of the persons from one another resides solely in the relationships which relate them to one another: “In the relational names of the persons the Father is related to the Son, the Son to the Father, and the Holy Spirit to both. While they are called three persons in view of their relations, we believe in one nature or substance.” Indeed “everything (in them) is one where there is no opposition of relationship.” “Because of that unity the Father is wholly in the Son and wholly in the Holy Spirit; the Son is wholly in the Father and wholly in the Holy Spirit; the Holy Spirit is wholly in the Father and wholly in the Son.” (Catechism of the Catholic Church, 255)
St. Gregory of Nazianzus, also called “the Theologian”, entrusts this summary of Trinitarian faith to the catechumens of Constantinople: 
Above all guard for me this great deposit of faith for which I live and fight, which I want to take with me as a companion, and which makes me bear all evils and despise all pleasures: I mean the profession of faith in the Father and the Son and the Holy Spirit. I entrust it to you today. By it I am soon going to plunge you into water and raise you up from it. I give it to you as the companion and patron of your whole life. I give you but one divinity and power, existing one in three, and containing the three in a distinct way. Divinity without disparity of substance or nature, without superior degree that raises up or inferior degree that casts down. . . the infinite co-naturality of three infinites. Each person considered in himself is entirely God. . . the three considered together. . . I have not even begun to think of unity when the Trinity bathes me in its splendor. I have not even begun to think of the Trinity when unity grasps me. (Catechism of the Catholic Church, 256)
In summary:  The mystery of the Most Holy Trinity is the central mystery of the Christian faith and of Christian life. God alone can make it known to us by revealing himself as Father, Son and Holy Spirit. (Catechism of the Catholic Church, (261)
The Incarnation of God’s Son reveals that God is the eternal Father and that the Son is consubstantial with the Father, which means that, in the Father and with the Father the Son is one and the same God. (Catechism of the Catholic Church, 262)
The mission of the Holy Spirit, sent by the Father in the name of the Son (John 14:26) and by the Son “from the Father” (John 15:26), reveals that, with them, the Spirit is one and the same God. “With the Father and the Son, he is worshipped and glorified” (Nicene Creed). (Catechism of the Catholic Church, 263)
“The Holy Spirit proceeds from the Father as the first principle and, by the eternal gift of this to the Son, from the communion of both the Father and the Son” (St. Augustine, De Trin. 15, 26, 47: PL 42, 1095). (Catechism of the Catholic Church, 264)
By the grace of Baptism “in the name of the Father and of the Son and of the Holy Spirit”, we are called to share in the life of the Blessed Trinity, here on earth in the obscurity of faith, and after death in eternal light (cf. Paul VI, CPG § 9). (Catechism of the Catholic Church, 265)
“In the name of the Father, and of the Son, and of the Holy Spirit. Amen.”