There are two equal and opposite errors into which our race can fall about the devils. One is to disbelieve in their existence. The other is to believe, and to feel an excessive and unhealthy interest in them. They themselves are equally pleased by both errors, and hail a materialist or a magician with the same delight.
Later in the book, the “senior” devil, Screwtape, tutors his “junior” charge, Wormwood, giving him advice on how to deceive the man he is supposed to lead into hell:
The fact that “devils” are predominantly comic figures in the modern imagination will help you. If any faint suspicion of your existence begins to arise in his mind, suggest to him a picture of something in red tights, and persuade him that since he cannot believe in that (it is an old textbook method of confusing them) he therefore cannot believe in you.
“The Great Deceiver” is a name Satan has well earned.