What is the theme in The Silver Chair by C. S. Lewis?

Like the other books in the Narnia series, God and Faith both server as themes that support each other. Jill does not know whom Aslan is when she first arrives in Narnia, although she has heard Eustace tell her stories of him. However, moments after arriving in Narnia, Jill must have faith that Eustace will not die when he falls from a cliff because Aslan has caught him with his breath. Jill must have faith that Aslan will not eat her when she goes to the stream to drink water.