Basil of Caesarea answers Amphilochius’s inquiry by defending the theological precision of Christian speech, especially the doxologies that give glory to the Father “with” the Son and Holy Spirit and “through” the Son in the Holy Spirit. He rejects attempts to assign “of whom,” “through whom,” and “in whom” exclusively to different divine Persons, arguing from Scripture that these expressions do not establish unequal natures or reduce the Son to an instrument. The Son’s eternal existence, shared majesty, unity of will with the Father, and saving titles all testify to his full divinity. Basil then argues that the Holy Spirit is likewise incorporeal, omnipresent, life-giving, sanctifying, eternal, and worthy of equal glory and worship. Baptism, creation, prophecy, Christ’s ministry, the Church’s gifts, and final judgment reveal the Spirit’s divine operations. “With the Spirit” expresses eternal equality and communion, while “in the Spirit” describes indwelling and illumination. Scripture, unwritten apostolic tradition, the sign of the cross, prayer facing East, and earlier Christian witnesses support this confession of three Persons in one God. Basil closes by defending the faith amid persecution, faction, and heresy, entrusting the Church’s understanding to the Holy Spirit.