Once back on the other side of the wardrobe, Edmund begins to feel sick from having eaten so much Turkish Delight. Lucy finds Susan and Peter, and announces that both she and Edmund have been to Narnia. Edmund maliciously tells them that he and Lucy had only been pretending to be in Narnia. Lucy rushes out of the room in tears, and Peter yells at Edmund for being so cruel to his sister. He says that he knows how Edmund is with the other children at school, always bullying those smaller than him. Susan mediates between the brothers, telling them that they should not be fighting at a time like this. After some time, they locate Lucy, who has been crying. Peter and Susan, worried that Lucy might be going mad, decide to talk to the Professor.
The next morning, Peter and Susan approach the Professor, certain that he will immediately contact their parents upon hearing their story. He invites them into his study and listens to their story from beginning to end, without interruption. When they are finished, the Professor, to their surprise, asks them why they are so certain that Lucy's story isn't true. He asks them to consider their own past experiences. Who, he asks, is more truthful: Lucy, or Edmund? He then advises them to use logic, lamenting, "Why don't they teach logic at these schools?" Logically, he says, Lucy is either telling lies, going mad, or telling the truth. He concludes that since Lucy is not a liar, and is not going mad, she must therefore be telling the truth. He acknowledges the fact that the house is very strange, and suggests that the door into Narnia is probably not a constant one. The other world, the Professor speculates, might well have a time frame far different from their own, which would explain why Lucy felt as though she had been gone for a long time, while no time at all had passed in their own world. Peter says that "if things are real, they're there all the time," but the Professor counters this assumption. In doing so, the Professor asks the reader to consider whether Lucy's willingness to believe in the possibility of alternate universes did, in fact, contribute to the creation of a real experience.
Days later, after talk of the wardrobe has ceased amongst the children, Mrs. Macready, the housekeeper, welcomes a group of adult tourists to the house, which is quite famous. Mrs. Macready leads the group through the house, telling the children to stay out of the way. The children decide to explore the house, but when they realize that they are about to run right into the tour group, they dart into the Wardrobe Room. They hear voices in the passageway, and, concerned that the tour group is about to enter the Wardrobe Room, rush to hide in the wardrobe. Peter, the last to enter, is careful not to shut the door behind them.
Edmund lies to Susan and Peter, refusing to corroborate Lucy's story about Narnia. In doing so, an interesting irony arises: Lucy, the more truthful of the two, is thought to be a liar, while Edmund, who is actually lying, is believed to be telling the truth. The reason for this misplaced trust lies in the fantastic nature of Lucy's story. The Professor, however, advises Peter and Susan to exercise logic: they should make their decision based on what they know to be true (Lucy is a truthful girl, and Edmund is not a truthful boy) and what they observe (Lucy is not mad). Hence, the logical conclusion is that Lucy is telling the truth. When the Professor - an adult whom they expect to greet the story with skepticism - entertains the possibility that Lucy is telling the truth, he opens up Peter and Susan's minds, thereby facilitating their entry into the world of Narnia.
Lewis uses Peter and Susan's conversation with the Professor to reveal that the journey through Narnia will serve as an alternative to the education that the children receive in school, and as an alternative to the reader's own education. As the Professor lectures Peter and Susan on the use of logic, he laments what is being taught in the schools. This critique of conventional education reveals Lewis's belief that children should learn to trust their instincts, even though the conclusions that they reach may seem fantastic. In this manner, Lewis sets the stage for all four of the children to enter Narnia.
The Professor's conversation with Peter and Susan is integral to the development of the narrative, as well as to the reader's own entrance into the world of Narnia. Readers are likely to identify with Peter and Susan more closely than with Lucy and Edmund: at the outset of the tale, they are likely to demonstrate a similar degree of skepticism about Lucy's tale. The conversation with the Professor is intended to drive home three crucial points: (1) one should trust one's own experiences; (2) one should make deductions based on one's own experiences; and (3) one should not immediately disregard a seemingly fantastic possibility based on a tenuous assumption (such as Peter's assumption that "real" things exist all the time). The Professor, in leading this conversation, becomes a physical manifestation of wisdom; he has already recognized the value in remaining open to the innate, unbiased knowledge displayed by children.
Furthermore, Lewis seems to be telling the reader that logic and faith are not fundamentally opposed to one another. In fact, logic can lead directly to a conclusion that requires faith to accept as true. Faith, in other words, can open a doorway to a profound experience that has the potential to alter an individual's very nature. As the narrative prepares to send all four children on a journey into Narnia, the reader is asked to prepare for the journey by suspending his or her doubts and allowing faith to act as a guide. Like the children, the reader is asked to make him or herself open to change.
A final note: Lewis offers his young readers a brief, practical lesson when he emphasizes the fact that Peter and Lucy are both careful to ensure that the wardrobe door does not shut behind them.