The Holy Trinity is one true God revealed as three distinct persons—Father, Son, and Holy Spirit—who share one single essence, substance, or nature (CCC 253). These three persons are one and the same God, remaining distinct yet inseparable in their divinity (CCC 261-263). This mystery indicates that while there are three persons, there is no opposition of relationship, and they form a unified whole (CCC 254-256).

Within this unity, the Father is recognized as the source and origin of the Trinity (CCC 2789-2790). The Son, who is the coeternal Word of God (CCC 266), is eternally begotten by the Father (CCC 2789-2790). The divinity of the Son is affirmed through His claim of oneness with the Father (John 10:30) and His role as the definitive Word of God in whom everything has been said (Hebrews 1:1-2).

The Holy Spirit is the third person of the Trinity, who is consubstantial with the Father and the Son and inseparable from them (CCC 689, CCC 243). The Spirit proceeds from the Father as the first principle and from the communion of both the Father and the Son (St. Augustine, De Trin. 15, 26, 47; CCC 246). The Holy Spirit is essential for the mission of the Trinity, as He reveals Christ to humanity and makes Him visible (CCC 690). Moreover, the knowledge of the Father is obtained through the Son, while the knowledge of the Son is obtained through the Holy Spirit (684).

The distinction between the persons exists in their relationships with one another, yet they are united by an infinite co-naturality as one divine essence (CCC 253). This means each person is fully God and is wholly present in the others. This divine unity is reflected in the joint mission of the Word and the Spirit (CCC 702) and in the combined works of God’s almighty love, which encompass the Father’s creation, the Son’s redemption, and the Holy Spirit’s sanctification.

For the Christian, the life of the Trinity is entered through Baptism, which communicates God’s life and unites the believer with the Father and the Son (683). Through this sacrament, Christians are called to worship one God in the Trinity and the Trinity in unity (Athanasian Creed: DS 75; ND 16). This Trinitarian life is expressed in prayer, which is primarily addressed to the Father (CCC 2680) but is made possible by the Father sending the Spirit of His Son into the hearts of believers, allowing them to cry out “Abba! Father!” (CCC 2766). In praying the “Our Father,” the believer confesses a communion with the Father and the Son in the one Holy Spirit, glorifying them together (CCC 2790).