2. The service of latria (B. III, Chap. CXX) is paid by holy men to God alone (Deut. vi, 13). But holy men pay that service to the Holy Ghost: for it is said: We who serve the Spirit as God (qui spiritui Deo servimus. -- Phil. iii, 3). And though some manuscripts have, We who serve in the spirit of the Lord (qui spiritu Domini servimus [showing the reading Theou]), yet the Greek manuscripts and the more ancient Latin ones have, We who serve the Spirit as God (qui spiritui Deo servimus); and from the Greek itself [latreuontes] it appears that this is to be understood of the service of latria, which is due to God alone.*
3. To sanctify men is a work proper to God: I am the Lord who sanctify you (Levit. xxii, 9). But it is the Holy Ghost who sanctifies, according to the words of the Apostle: Ye are washed and sanctified and justified, in the name of our Lord Jesus Christ and in the Spirit of our God (1 Cor. vi, 11).
4. As the life of the body is by the soul, so the soul's life of justice is by God: hence the Lord says: As the living Father hath sent me, and I live by the Father, so whosoever eateth me, the same shall also live by me (John vi, 58). But such life is by the Holy Ghost; hence it is added: It is the Spirit that giveth life (John vi, 63): and the Apostle says: If with the spirit ye mortify the deeds of the flesh, ye shall live (Rom. viii, 18).*
7. The Spirit searcheth all things, even the profound things of God. For what man knoweth the things of a man but the spirit of man that is in him? So the things also that are of God no man knoweth but the Spirit of God (1 Cor. ii, 10, 11). But to comprehend all the profound things of God is not given to any creature: for no one knoweth the Son but the Father, nor doth any one know the Father but the Son (Matt. xi, 27); and in the person of God it is said, My secret to me (Isai. xxiv, 16). Therefore, the Holy Ghost is, not a creature.
8. According to the above comparison, the Holy Ghost is to God as a man's spirit to man. But a man's spirit is intrinsic to man, not of a foreign nature, but part of him. Therefore the Holy Ghost is not of a nature extrinsic to Deity.
11. Evidently from Holy Scripture it was God who spoke by the prophets, as it is said: I will hear what the Lord God speaketh in me (Ps. lxxxiv, 9). But it is equally evident that the Holy Ghost spoke in the prophets: The Scripture must be fulfilled, which the Holy Ghost foretold by the mouth of David (Acts i, 16). The holy men of God spoke, inspired by the Holy Ghost (2 Pet. i, 21). Clearly then the Holy Ghost is God.
17. The Holy Ghost is expressly called God in the text: Ananias, why hath Satan tempted thy heart to lie to the Holy Ghost? . . . . Thou hast not lied to men, but to God (Acts. v, 3, 4).
23. Now there are diversities of graces, but the same Spirit. And there are diversities of ministries, but the same Lord. And there are diversities of operations, but the same God, who worketh all in all. . . . But all these things one and the same Spirit worketh, dividing to every one according as he will (i Cor. xii, 4 5, 6, 11). This text clearly declares the Holy Ghost to be God, as well by saying that the Holy Ghost works what it has previously said that God works, as also by the declaration of His working according to the arbitrement of His own will.*
4.12 : How the Son of God is called the Wisdom of God
4.18 : That the Holy Ghost is a Subsistent Person