36 Having thus concluded that we must reject the word 'creation' from our confession of faith in God the Only-begotten, we proceed to lay down the teachings of reason and of piety concerning the Holy Spirit, that the reader, whose convictions have been established by patient and earnest study of the preceding books, may be provided with a complete presentation of the faith. This end will be attained when the blasphemies of heretical teaching on this theme also have been swept away, and the mystery, pure and undefiled, of the Trinity which regenerates us has been fixed in terms of saving precision on the authority of Apostles and Evangelists. Men will no longer dare, on the strength of mere human reasoning, to rank among creatures that Divine Spirit, Whom we receive as the pledge of immortality and source of fellowship with the sinless nature of God.
Source: On the Trinity (New Advent)