Basil's argumentation defending the divinity of the Holy Spirit addresses the unity of the Godhead and the eternal associations of the Holy Spirit to the Father and the Son within the Holy Trinity (Basil 60). Not only does this augment his defense of the Holy Spirit, it completes St. Basils' trinitarian theology thereby laying the foundations of Orthodox Christian Trinitarian theology.
The Holy Trinity
The unity of the Godhead is reflected in the works of the Holy Trinity. Whether regarding creation or human redemption, the works of the Holy Trinity are always one, revealing the communion of Father, Son and Holy Spirit. A good example of this unity of action is in the creation of the angels. These pure, spiritual and transcendent powers are called holy because they receive their holiness from the Holy Spirit. In considering the angels, or any other creature, it is best to think of the Father as the cause of all that exists. Then one should think of the Son, Who is their creator, and the Holy Spirit Who is their perfecter. The angels exist, therefore, due to the will of the Father and are brought into being through the work of the Son. They are perfected by the presence of the Holy Spirit since they persevere in the holiness which comes from Him. The Originator of all things is One, creating through the Son and perfecting through the Holy Spirit (Basil 61).
The Father's work is perfect since He achieves all in all. The Son's handiwork is not deficient if not completed by the Holy Spirit. The Father creates through His will alone and needs not create through the Son, but chooses to do so. Similarly, the Son works as the Father's likeness and needs no further cooperation, choosing to complete His work through the Holy Spirit. Psalm 32:6 reveals this divine cooperation, "by the word of the LORD were the heavens made; and all the host of them by the Spirit of His mouth." The Word is not mere speech, but He who was with God in the beginning (John 1:21). The "Spirit of His mouth" is not mere exhalation but the Spirit of truth Who proceeds from the Father (John 15:26). Behold these three: the Lord dictates, the Word creates, and the Spirit strengthens (Basil 62). Such voluntary cooperation reveals both the divinity of the Holy Spirit and the unity of the Godhead in creation (Basil 62).
In demonstrating divinity of the Holy Spirit through His redemptive works, St. Basil also illustrates the unity of the Holy Trinity's redemptive work. By nature, the Holy Spirit is good, as is the Father and the Son. Creatures wishing to share in goodness, on the other hand, must choose to do so. The Holy Spirit searches the depths of God, whereas creatures receive divine illumination only through the Spirit. The Holy Spirit gives true worshippers the knowledge of God personally, or in Himself. For believers, divine knowledge comes through the Holy Spirit since the way to such knowledge ascends from the Holy Spirit to the one Son to the one Father (Basil 74,75). Likewise, goodness, holiness, and royal dignity reach from the Father through the Son to the Holy Spirit. Therefore believers share in divine knowledge and goodness in the Holy Spirit and all three persons of the Holy Trinity participate in human illumination and sanctification. The Holy Spirit gives life to all, together with the Father Who enlivens all things and the life-giving Son. Goodness, illumination, holiness, and resurrection come from the cooperative work of the Holy Trinity, demonstrating both the divine dignity of the Holy Spirit and the unity of the Godhead (Basil 75)
The Godhead in three persons is one God, sharing one divine essence. Arguing against anyone who would subordinate the Holy Spirit regarding the divine essence, St. Basil cites the baptismal command of the Lord, "go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit ... " (Mat. 28:19). Here the Lord ranks Father, Son and Holy Spirit together unambiguously. This reveals the divine dignity of the Holy Spirit and the ranking of all three as equal regarding the divine essence. According to (Basil 70), this is not an example…