I am Rahim.
I am writing a thesis on Lewis. I came across John Beversluis 'C.S. Lewis and the Search for Rational Religion'. He is showing Lewis like a amateur thinker who has many flaw. Could you give me some advice ?
Rahim: The first thing I would have to ask you is what version of Beversluis's book you have. The first version had a red cover, was published by Eerdmans press, and came out in 1985. The second came out in 2007 and was published by Prometheus Books. I differ with the conclusion of both editions, since he is an unbeliever who thinks that Lewis's apologetics are entirely unsuccessful. However, the second edition is considerably fairer than the first, and takes into account the criticisms of his book that were written by a number of people, including myself.
Secondly, you have to calibrate your expectations of Lewis in a reasonable way. Lewis got the best philosophical education there was to be had as a student of Greats at Oxford in the 1920s, and to my mind is an unusually insightful thinker. However, his career was in Medieval and Renaissance Literature, and so he didn't follow, and respond to, philosophical developments the way a philosophy professional world. He wrote only three book-length works, Mere Christianity, The Problem of Pain, and Miracles, which could be regarded as apologetic books per se. So in one sense, sure, you'd have to regard him as an amateur, if the contrast class is professional. You cannot expect the kind of technical philosophical work that you get from a Plantinga or even a Craig.
For example, Lewis's definition of naturalism isn't adequate, and so I use an account from William Hasker's The Emergent Self, which doesn't have some of the problems that Lewis's does. But that is the sort of thing you have to do when you are dealing with someone whose ideas you like, but who isn't operating in the "contemporary analytic philosophy" mold.
My book is, among other things, a response to the 1985 book. The book C. S. Lewis as a Philosopher (ed. Baggett and Walls, IVP) has some good material, including two discussions of Beversluis by Horner and Baggett. Although, once again, they are addressed to the 1985 edition.
I have been meaning to write a detailed review of the new book, but I haven't found the time yet.