I'm currently reading The Lion, the Witch, and the Wardrobe again and just reached the point where Peter and Susan tell the Professor about Lucy's stories of Narnia. They're confused because Lucy seems to be making up strange stories, even though she's not crazy and has always been truthful. The Professor then says,
"Why don't they teach logic at these schools? There are only three possibilities. Either your sister is telling lies, or she is mad, or she is telling the truth."
Glad I'm able to catch these apologetic details this time around :)