I recently started reading Mere Christianity, and I am trying to figure out Lewis's view on whether morality is taught or is something that every person knows by nature. He seems to claim both views, and I am trying to figure out how he reconciles them (or if I have just misunderstood something).
In chapter 1 ("The Law of Human Nature"), Lewis states the following:
This law was called the Law of Nature because people thought that every one knew it by nature and did not need to be taught it. They did not mean, of course, that you might not find an odd individual here and there who did not know it, just as you find a few people who are colour-blind or have no ear for a tune. But taking the race as a whole, they thought that the human idea of decent behaviour was obvious to every one. And I believe they were right.
Then in chapter 2 ("Some Objections"), Lewis addresses an objection that the Law of Nature is just a social convention "that is put into us by education." He responds with the following:
The people who ask that question are usually taking it for granted that if we have learned a thing from parents and teachers, then that thing must be merely a human invention. But, of course, that is not so. We all learned the multiplication table at school. A child who grew up alone on a desert island would not know it. But surely it does not follow that the multiplication table is simply a human convention, something human beings have made up for themselves and might have made different if they had liked? I fully agree that we learn the Rule of Decent Behaviour from parents and teachers, and friends and books, as we learn everything else.
He then goes on to explain why the Law of Nature / Moral Law / Rule of Decent Behavior falls into the same category as mathematics, being a real truth instead of a convention.
On the surface, it seems like Lewis is making opposing statements: first that this moral law is intrinsically known by humans without being taught and second that it is something that is in fact taught. My guess at this point is that he sees our sense of right and wrong as a faculty that must be developed. While we may know the principles of morality as children, we do not know all of the applications of those principles and must be taught. And perhaps it is a sense that can become sharpened or dulled, so good teaching could sharpen it.
That's how I would reconcile those statements based on how in the first quote someone without moral knowledge is likened to someone with an impaired sense. But that may just be the way I would explain it, and I'm not confident that that is actually the way he would explain those statements. Perhaps there is something that is so obvious to him (and everyone else in the world since his target audience was all of the UK) that it goes without saying, and I have completely missed it.
So if anyone has any insights into what Lewis has said or would say on how morality is inherently known while also being taught, please share. Thanks!