2 Therefore though our discourses concerning the Holy Ghost are divided, yet He Himself is undivided, being one and the same. For as in speaking concerning the Father, at one time we taught how He is the one only Cause; and at another, how He is called Father, or Almighty; and at another, how He is the Creator of the universe; and yet the division of the Lectures made no division of the Faith, in that He, the Object of devotion, both was and is One—and again, as in discoursing concerning the Only-begotten Son of God we taught at one time concerning His Godhead, and at another concerning His Manhood, dividing into many discourses the doctrines concerning our Lord Jesus Christ, yet preaching undivided faith towards Him—so now also though the Lectures concerning the Holy Spirit are divided, yet we preach faith undivided towards Him.
For it is one and the Self-same Spirit who divides His gifts to every man severally as He will, Himself the while remaining undivided. For the Comforter is not different from the Holy Ghost, but one and the self-same, called by various names; who lives and subsists, and speaks, and works; and of all rational natures made by God through Christ, both of Angels and of men, He is the Sanctifier.
Source: Catechetical Lectures (New Advent)