Read “Mere Christianity”, Lewis clearly identifies A natural and supernatural world. Such a world view is the foundation of Christianity.
Trust me I have read it. Numerous times. Yes, he uses the language and the terminology because that’s what hs people understand, but in one of his lesser known works (I don’t recall which at present), he discusses those terms at length and questions them. He illustrates his point with the miracle at Caana where Christ turned water into wine. He pointed out that the same occurrs in nature (with the intervention of a grape vine, a vintner and time, etc.) but that water can be turned into wine. We view the grapevine, vintner route as, ‘natural,’ because that is the scope of our worldly experience, but just because something occurs outside the scope of our experience does not mean it is unnatural. To the believer that truly understands God can do all things, nothing should be considered outside the realm of possibility be it turning water into wine, parting the Red Sea, etc. In fact, to those who believe in the possibility of Divine intervention, such things should be considered perfectly natural.