Last month I got this reply on the comment line from Ed Babinski.
Lewis fleshed out Chesterton's previously fallacious argument that Jesus was divine because he said so in the Gospel John, and hence Jesus would have been a liar, a madman or "worse" [Chesteron] to have lied about such a thing. False trilemma. Both Chesterton and Lewis skipped right over any and all specific questions that theologians have regarding whether Jesus ever said such things. Have you read Is John's Gospel True? by Maurice Casey; or Howard Teeple's The Literary Origin of the Gospel of John? Or take James D. G. Dunn's latest two works on Jesus in which he likewise comes down against Jesus having said the things found in the fourth Gospel. Dunn is a well known theologian (and a moderate with some liberal tendencies) who concludes with other moderate and liberal scholars that Jesus never said a word in the Gospel of John. There are many specific arguments, but one thing to note is that Jesus in the fourth Gospel doesn't utter a single parable and speaks to people constantly about himself, using an "I am" formula time and again, and even disagrees with what he said in the other three Gospels about direct forgiveness in the Our Father, and about how to inherit eternal life. Instead, in the fourth Gospel Jesus changes his tune in a secret nightime meeting with Nicodemus, and introduces a new word about the absolute necessity of having to be "born again" and to believe such and such about Jesus, or be "damned already." Chesteron and Lewis were both ignorant of such questions, and and simply assumed the fourth Gospel picture of Jesus of Nazareth was true, even central! Thus they ignored the questions that even in their day were being asked, and that continue being asked today. See Peter Amue's list of theological works on the Gospel of John from major university presses: http://www.amazon.com/exec/obidos/tg/listmania/list-browse/-/2O7WERBN6M4K2/ref=cm_lm_detail_ctr_full_3/102-5977177-7502511
Interestingly enough, this is one of Pittenger's complaints against Lewis, and Lewis answered it as follows in God in the Dock (Eerdmans) p. 180. He was aware of higher-critical views on the Fourth Gospel and he offered reasons for why those reasons were inadequate. He didn't just assume that the Fourth Gospel is reliable, as Babinski claims. He also points out that the case for the trilemma does not rest exclusively on the Fourth Gospel. He writes:
I confess, however, that the problem of the Fourth Gospel raises in me a conflict between authority and private judgment: the authority of all those learned men who think that Gospel unhistorical, and my judgment as a literary critic whcih constrains me to think it at least as close to the facts as Boswell's Johnson
. If I venture here to follow judgment in the teeth of authority, this is partly because I could never see how one escaped the dilemma aut deus aut malus homo by confining himself to the Synoptics. Moderns do not seem started, as his contemporaries were, by the claim Jesus makes to forgive sins; not sins against Himself, just sins. If Dr. Pittenger told me that two of his colleagues had lost him a professorship by telling lies about his character and I replied, "I freely forgive them both', would he not think this an impertinence (both in the old and the modern sense) bordering on insanity? And of course all three Synoptics tell the story of One who, at his trial, sealed His fate by saying He was the Son of God.