Together with a friend, I decided to read through C.S. Lewis' Mere Christianity. To be sure, it is a respected and often referenced piece of apologetic literature. Thus I approached it with high hopes - not that I expected it to convert me to Christianity or even make me slightly more partial to considering Christian doctrines as 'potentially true'.
What I find is a pretty sophomoric level of sophistication. Lewis even stoops as low as virtual ad hominem responses to arguments. A lot of his arguments rely on lack of imagination, essentially 'false dilemmas' or even false trilemmas. Simply put, God can only be a certain way because that's the only way Lewis can imagine him. God must have been this way, because Lewis cannot imagine anything else. Thus Lewis sets his own mind up to be the meta-God by which any God must adhere.
A major conceit is present already in the title - and it's a conceit that later on is glossed over with a sprinkle of ad hominem. To spell out in detail what conceit I am referring to, it is the very notion of 'mere Christianity'. Lewis claims to express the most rudimental, fundamental parts of Christianity - these are the stances you at least need to hold to be a Christian. Yet, in the very first part of the book, he admits to the existence of Christians that do not hold them, and his argument for rejecting them is nothing but name-calling: Christianity and water. Their Christianity is dilute - that's given as an assertion or even an axiom, with no actual argument backing it up.
This bodes ill for the intellectual standards of apologetics from Lewis' day onwards.
Lewis was fond of a form of the argument from morality. However, his lack of logic is quite evident as he rejects the notion that morality could be a form of herd instinct. He argues that morality is somehow clearly external to instinct [1, p. 10]. This he does by illustrating that morality is what triggers instincts and even strengthens some of them, and thus cannot be itself an instinct. I find this a weird argument with flawed premises: he assumes some kind of clear-cut hierarchy of things in the mind that also happens perfectly to correspond to our terminology for these things in the mind. For this to work, the instincts have to be objects of the exact same type, and in the exact same place in some hierarchy in the mind. There's no reason to believe that instincts really are as clear-cut as that, but Lewis probably believed in a created universe that was designed in a very organized manner. Using the un-established fact that the universe is like that to prove that the universe is created is begging the question.
I shall post a series of posts dissecting the fallacies of Lewis' magnum opus in apologetics, a book still considered one of the greatest defenses of Christian faith.