I have met people who .... 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. There is no difference of moral principle here: the difference is simply about matter of fact. It may be a great advance in knowledge not to believe in witches: there is no moral advance in not executing them when you do not think they are there. You would not call a man humane for ceasing to set mousetraps if he did so because he believed there were no mice in the house.Fortresses of cogent apologetic arguments should be made of sterner stuff -- preferably of stuff not quite so chillingly insouciant in its embrace of burning women to death for imaginary offenses. And speaking on behalf of one of my many pet peeves, it would improve this passage if it didn't contain yet another instance of a Christian issuing factual declarations ("we do not believe there are such things") that contradict the plain declarations of the Bible (kill the witches!).
Lewis almost achieves a very important insight when he acknowledges that matters of fact are salient in moral judgments -- do witches exist or not? is there a god watching and taking notes about everything we do or think, or is there not? -- but then takes it away with the baffling assertion that "there is no moral advance in not executing [witches] when you do not think they are there." To the contrary, there is very obviously a moral advance in not executing or otherwise mistreating people based on factually false accusations, whether of witchcraft or anything else.
Mere facts matter to questions of what is right and just, an insight of special relevance now as the US Supreme Court considers arguments and assertions bearing on the legal status of another long-vilified category of persons the Bible summarily condemns (kill the gays!). The justices will do well to start with mere facts, carefully distinguishing those from stereotypes, conventions, prejudices, and myths from wretched old books.