This study seeks to illuminate the irreducibly biblical character of Augustine's mature Christology through a close study of his Tractates on the Gospel of John (In Iohannis Evangelium Tractatus CXXIV). The first chapter serves as an introduction and basic consideration of the status quaestionis with regard to the study of Augustine's Christology. This background provides the necessary context for clarifying the importance of a closer investigation of Augustine's preaching about Christ. The second chapter turns to a close sequential study of the text of Augustine's preaching on the Gospel of John, beginning from his unified interpretation of the prologue as a unique exposition of the incarnational framework of the Gospel as a whole. It is demonstrated that this focus upon the normativity of the prologue and its proclamation of the wholeness of Christ in both humanity and divinity (totus Christus) functions as a guiding principle for Augustine's understanding of the complexity of the Gospel narrative concerning the Incarnate Word.The third chapter analyzes those portions of Augustine's homiletic commentary that focus upon episodes in the Gospel where Christ teaches particularly about the nature of his divinity. Throughout Augustine's preaching, he identifies the narrative of the Gospel as essential to revealing Christ's divinity because of the way it presents the real condescension of the Word. In a complementary manner, chapter four studies the manner in which Augustine identifies other portions of the Gospel as revealing the true nature of Christ's humanity as the "way" to his divinity. The complexity of this concept helps clarify Augustine's interpretation of Christ's human weakness and limitation as a function of God's mercy, and illuminates his mature understanding of the revelatory and soteriological function of Christ's humanity. The fifth chapter rounds out the study by examining the manner in which Augustine's Christology is intimately connected with his ecclesiology in the Tractates. Christ's union with his members is essential to a complete understanding of the way in which the wholeness of Christ's person expresses the ultimate end and purpose of the condescension of the Word in the Incarnation. The concluding chapter clarifies that Augustine's exegesis argues that this wholeness is achieved in no other way than through the embodied mediation of Christ's entire life.