CCC 254
© Libreria Editrice Vaticana Source: vatican.va
The divine persons are really distinct from one another. "God is one but not solitary." Fides Damasi: DS — Denzinger–Schönmetzer (Enchiridion Symbolorum). "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." Council of Toledo XI (675): DS — Denzinger–Schönmetzer (Enchiridion Symbolorum):25. 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." Lateran Council IV (1215): DS — Denzinger–Schönmetzer (Enchiridion Symbolorum). The divine Unity is Triune.
Read the full chapter 1. I Believe in God the Father ¶198–421