Quote 1
"If there really is a door in this house that leads to some other world […] I should not be at all surprised to find that that other world had a separate time of its own; so that however long you stayed there it would never take up any of our time. On the other hand, I don't think many girls of her age would invent that idea for themselves. If she had been pretending, she would have hidden for a reasonable time before coming out and telling her story."
"But do you really mean, Sir," said Peter, "that there could be other worlds – all over the place, just round the corner – like that?"
"Nothing is more probable," said the Professor. (5.38-40)
The Professor surprises Peter and Susan by using logic to argue for the possibility that supernatural occurrences might take place – that parallel worlds could really exist, and that Lucy might have been to one.