In his influential, albeit controversial, book The Testament of Jesus, Ernst Kasemann presents a provocative analysis of the Gospel of John, particularly focusing on Chapter 17 (Jesus' Farewell Prayer) as a summary of Johannine theology. Käsemann's central argument is that the Fourth Gospel, as it stands, is highly docetic, meaning its presentation of Jesus emphasizes his divine nature to such an extent that his genuine humanity is diminished. In essence, Käsemann used the "farewell prayer" to argue that the Gospel of John exhibits an overly realized, or naive, Christology that potentially compromises the reality of the Incarnation and the historical grounding of the Christian faith. The book forces readers to engage with the tension between the historical Jesus and the theological presentations found in the New Testament texts.