This book meticulously explores Narsai's life, literary legacy, and the historical theological landscape of the East Syrian tradition, with a particular focus on his comprehensive pneumatology. It traces the concept of the Holy Spirit from Syriac biblical interpretations and early Syriac writings through the contributions of figures like Aphraates and Ephrem, culminating in Narsai's profound understanding of the Trinity, the Spirit's role in Christ's salvific economy, and its active presence in the Church and its sacraments of Baptism, Eucharist, and Priesthood. This scholarly work offers a deep synthesis of Narsai's thought, situating him as a crucial voice in the development of East Syrian Christian theology.