Chapter 10 — Part I: The Creed — Article VIII: I Believe in the Holy Ghost
Section 7. But as the production of the Third Person has no proper name, but is called spiration and procession, the Person produced is, consequently, designated by no proper name. His emanation has no proper name simply because we are obliged to borrow from created objects the names given to God and know no other created means of communicating nature and essence than that of generation. Hence we cannot discover a proper name to express the manner in which God communicates Himself entire, by the force of His love. Wherefore we call the Third Person Holy Ghost, a name, however, peculiarly appropriate to Him who infuses into us spiritual life, and without whose holy inspiration we can do nothing meritorious of eternal life.