Ed Babinski wrote a rather lengthy reply on matters related to the trilemma on the comments line. In fact, it went for 15 pages when I downloaded it onto Word.
Let me begin with his discussion of Lewis's comparison of the Gospel of John with Boswell's Johnson. On the one hand, I am prepared to agree with Babinski that the Boswell comparison is not especially helpful. I think what is right about it is this: A commentator on John had called John a "spiritual romance," which prompted Lewis to ask, famously "How many romances has that man read." He then said that it either had to be the case that the whole thing was reportage on the order of Boswell's Johnson or it someone in the Second Century had to to have invented the modern realistic novel, which was unknown in those times. He was trying to claim that the Gospel is realistic rather than fictional in form, and I think that is correct.
In my own field of philosophy we have an example that I like a lot better, the dialogues of Plato. Now I don't know what Lewis thought in the area of Plato scholarship, but I'm inclined to think that the earliest dialogues represent the historical Socrates, since in these Socrates is mainly asking questions and is not pontificating detailed theories. As we go along, we find more theorizing, and the interlocutors start dropping out of the picture, often saying little more than "Yes, Socrates." When this starts happening, I think Plato has taken over. But even in these cases, there is a historical core. In the Republic, for example, there is a lot of interesting exchange with Thrasymachus and Plato's brothers, and then you get a lot of theorizing.
I think it's a lot easier to defend the claim that there is a historical core in John which has gets expanded than to defend the claim that the whole thing is accurate reportage. (Of course you can believe by faith that it's inerrant, but that's another matter).
What I suspect, however, is that Ed is trying to discredit Lewis because of this inapt comparison, that it goes to show that Lewis really didn't grow up intellectually, etc. And if this is really what is going on here, then I find it simply tiresome. I think Lewis was on the right track in most of what he wrote, I have never denied that he sometimes misfires, and I said "Great thinkers are always the ones that make us think harder for ourselves, not thinkers that do our thinking for us." (CSLDI p. 14).
A lot of people attempt to discredit Lewis by finding something that he said that seems silly to them and harping on it. This is a procedure that I have little patience for. If I were asking people to accept claims on Lewis's authority (Jack said it, I believe it, that settles it) that would be one thing, but I can't see how anybody can think that who has read my writings at all carefully.