Lewis says that he will not discuss the differences in doctrine between the various Christian sects for two reasons: the second reason, is this:
Lewis confesses that the doctrinal disputes between Christian denominations are more likely to turn someone away than cause him to convert – so hide these disputes from people who are considering Christianity. This behaviour is just deceptive.And secondly, I think we must admit that the discussion of these disputed points has no tendency at all to bring an outsider into the Christian fold. So long as we write and talk about them we are much more likely to deter him from entering any Christian communion than to draw him into our own. Our divisions should never be discussed except in the presence of those who have already come to believe that there is one God and that Jesus Christ is His only Son
This is analogous to a person who buys a house because a real estate agent failed to disclose that it was built on the site of a flood prone area or was riddled with termites. This guy is lying already, I hope it gets better than this. Moving onto the main book;
Book 1 Right and Wrong as a Clue to the Meaning of the Universe
1. The Law of Human Nature
On the 3rd page of my book he states;
This demonstrably incorrect. How can anyone claim that all societies throughout history have had essentially the same moral code? Has Lewis never heard of the polygamy of the Mormons, Arab and ancient Greek paedophilia, Aztec human sacrifice, female genital mutilation in the Middle East, Islamic "honour killings”, and oppression of women? The Bible itself has nothing against polygamy, slavery, child abuse or discrimination against the handicapped, in fact it recommends them! How about racism, intolerance and genocide? It is clear that all societies do not have the same unchanging moral law.I know that some people say the idea of a Law of Nature or decent behaviour known to all men is unsound, because different civilisations and different ages have had quite different moralities.
But this is not true. There have been differences between their moralities, but these have never amounted to anything like a total difference. If anyone will take the trouble to compare the moral teaching of, say, the ancient Egyptians, Babylonians, Hindus, Chinese, Greeks and Romans, what will really strike him will be how very like they are to each other and to our own
Things like murder and theft, do not need God to explain them, they had been around for thousands of years before Judaism. If there is no universal Law of Nature, or unchanging universal moral laws then Lewis’ argument for the existence of God collapses.