Roman Catechism 10.17

Chapter 10 — Part I: The Creed — Article VIII: I Believe in the Holy Ghost

Section 17. The Holy Ghost Is Distinct From The Father And The Son — The pastor should also accurately explain to the faithful that the Holy Ghost is not only God, but that we must also confess that He is the Third Person of the Divine Nature, distinct from the Father and the Son, and produced by Their will.