C.S. Lewis: Has People's Sense of Right and Wrong Changed Noticeably?

Lewis' argument mainly relies on the idea that our sense of morality is universal and that this proves that some kind of God must have existed. However, he responds to an objection regarding apparent changes in morality. He states the objection to his argument as such:

I conclude then, that though the difference between people’s ideas of Decent Behaviour often make you suspect that there is no real natural Law of Behaviour at all, yet the things we are bound to think about these differences really prove just the opposite. But one word before I end. I have met people who exaggerate the differences, because they have not distinguished between differences of morality and differences of belief about facts. For example, one man said to me, ‘Three hundred years ago people in England were putting witches to death. Was that what you call the Rule of Human Nature or Right Conduct?’ But surely the reason we do not execute witches is that we do not believe there are such things. If we did—if we really thought that there were people going about who had sold themselves to the devil and received supernatural powers from him in return and were using these powers to kill their neighbours or drive them mad or bring bad weather—surely we would all agree that if anyone deserved the death penalty, then these filthy quislings did? [1, p. 14]

Although it might seem I quoted way too much, we will find there are reasons for that - I find problems in most parts of this paragraph.

Although I thinkby presenting this objection in the context he did and phrasing it the way he did, Lewis made it seem more silly than it really is, I find myself still sympathizing with the sentiment in the argument even in its apparently naive form. Lewis counter-argument just goes to show how bad he was at thinking about things.

By attracting our attention to one of the most obvious examples - witch-burnings - he makes the case easy for himself (because if they really had existed, they would indeed have been terrible beings) but also makes us forget about all the less obvious examples (which would be greater evidence of moral differences). We have not stopped believing murderers exist, yet many people have stopped considering death penalty for murderers justifiable. Another example is sodomy, which in Britain was punished by death as recently as 1835.

We still believe 'sodomites' exist. Thus there's a problem for Lewis' argument here – to state his explanation analogously, we get

But surely the reason we do not execute gay people is that we do not believe there are such things.

clearly, this is nonsense of the highest order. Picking an obvious yet rather specific example makes it easy for Lewis to shrug this important problem off. No, clearly it should be more like

But surely the reason we do not execute gay people is that we believe it to be wrong to do so, and people in former times had a different sense of right and wrong.

Let us visit another issue, viz. that of differences of morality vs. differences of belief about facts. If the morality of an action relies on the beliefs about facts involved, would not very many quite appalling crimes turn out morally acceptable? Would not even an antisemitic act of murder, carried out in the belief that all Jews are conspiring against all of mankind, be morally sound - just factually mistaken?

Clearly there's a difference in the morality of someone who also is a skeptic, and therefore ensures that his judgments of people is based on reasonably well established facts or not from the morality of someone who just goes gung-ho with whatever pretend-knowledge has been thrown their way.

Lewis understanding of this issue is so weak that I wonder what justification there really is for calling him an 'intellectual giant'. If that is an apt description, he must have been quite the stumbling intellectual giant.