The book is a retelling of the Greek myth of Cupid and Psyche, as told by Orual, Psyche’s older sister. In one scene Psyche tells Orual of the longing she has in her soul.
“I have always — at least, ever since I can remember — had a kind of longing for death.” (Psyche)
“Ah, Psyche,” I said, “Have I made you so little happy as that?” (Orual)
“No, no no. You don’t understand. Not that kind of longing. It was when I was happiest that I longed most. It was on happy days when we were up there on the hills, the three of us, with the wind and the sunshine … where you couldn’t see Glome or the palace. Do you remember? The colour and the smell, and looking at the Grey Mountain in the distance? And because it was so beautiful, it set me longing, always longing. Somewhere else there must be more of it. Everything seemed to be saying, Psyche come! But I couldn’t (not yet) come and I didn’t know where I was to come to. It almost hurt me. I felt like a bird in a cage when the other birds of its kind are flying home. (Psyche)
“The sweetest thing in all my life has been the longing — to reach the Mountain, to find the place where all the beauty came from — my country, the place where I ought to have been born. Do you think it all meant nothing, all the longing? The longing for home? For indeed it now feels not like going, but like going back.” (Psyche)
The Apostle Paul with eloquence and simply merely says:
But our citizenship is in heaven. And we eagerly await a Savior from there, the Lord Jesus Christ, who, by the power that enables him to bring everything under his control, will transform our lowly bodies so that they will be like his glorious body. — Philippians 3:20-21
Indeed, as Lewis says, we mortal creatures will outlive creation!