The Fool had not been convinced of the validity of Christian beliefs by his first reading of Mere Christianity, so he decided that he had better read it again. The Fool does not question Lewis' conversion to Christianity, and he is quite overwhelmed with his intellect, imagination, and ability to write fiction. But the Fool doubts that Lewis ever was a convinced and dedicated agnostic or atheist. As a youth he had an apparent fascination with elaborate systems of mythology, and his later fiction, the Narnia saga and stories of the planets, is filled with poetic symbols of power and morality. It is a small step from contemplating a deity to bowing before it.
Different rooms leading off the hall are the different denominations.
He said that he is not primarily concerned about which room Christians occupy, but he is concerned about getting them into the hall. The Fool realized the second time around that Lewis might have been writing to the people in the rooms, and possibly even to those in the hall, but the Fool found no convincing reasons to move into the hall from outside the house, and certainly nor into any of the rooms, on the book's account. For instance, either the Virgin Birth is valid or it is not. Either it is essential to Christian Belief or it is not. Lewis discusses and then avoids conclusions about such issues as being too controversial.