The Lion, the Witch, and the Wardrobe, chapter 2
Even as he expands the story beyond the parameters of the world we know, introducing us to talking, mythical beasts, Lewis grounds the identity of humanity in Adam and Eve. "Should I be right in thinking that you are a Daughter of Eve?" This is one of the ironies of reading fantasy and fiction: it can show us reality more clearly.
Lewis continues playing with this paradox, as Tumnus the fawn is quite provincial in his thinking, even as he expands the world we know. Tumnus thinks Wardrobe is a country. He has books on his shelf like "Is Man a Myth?" They have tea.
Being provincial or having wrong ideas about things doesn't prevent one from being kind-hearted and delightful. It also shouldn't define the antithesis: how we define what team we are on, good guys or bad guys. We discover Narnia has bad guys, by the way. Neither Narnia nor our world is a Thomas Kinkade painting with no evil in it. Tumnus has a secret. About a witch. Narnia has a darker side that Lucy experiences as they rush back to the lamppost. Is Tumnus a delightful faun, or a "kidnapper for the witch"?
Well, Tumnus has a book on his shelf that questions the existence of men, whom the prophecies say must sit on the thrones of Cair Paravel to right what is wrong. I surmise Lewis means this as a parallel to modern scholars who question what Jesus really said or the veracity of fulfilled OT prophecy. Surely for having such a book Tumnus is a heretic, and Lucy should renounce him! Lewis in the character of Tumnus is mixing opposite perspectives - the provincial and the overly liberal - and showing that a great deal of both can be tolerated when one sides with the right by his actions, which in turn reveal his faith, as Tumnus helps Lucy home.