What was the main idea in Faintly Macabre’s story that she told?

Milo’s archetypal heroic journey continues, and in these chapters he actually seems to get another call and an opportunity to answer it. After getting thrown in jail for disrupting the marketplace, he learns from Faintly Macabre about the tensions in the kingdom of Wisdom due to Azaz and the Mathemagician’s dispute over the supremacy of words or numbers. When he hears about the princesses Rhyme and Reason he suggests he might try to rescue them.