The Divided Line guidebook explores the philosophical bases behind the concepts introduced in the novel. These include the philosophies of Socrates, Plato, Aristotle, Averroes, Hypatia, Democritus, Heraclitus, Plotinus, Marsilio Ficino, and René Descartes, as well as the ideas, beliefs, and works of Leonardo da Vinci, Michelangelo, Queen Christina of Sweden, Princess Elisabeth of Bohemia, Sigmund Freud, Carl Jung, and Arthur Schopenhauer.

This guidebook can be used by instructors, but it has been written to be accessible to the students themselves so that they can delve deeper into the philosophical content that is the basis for the novel. It provides for each chapter a summary of the plot developments, a philosophical basis for the key concepts in the chapter, discussion questions, and suggestions for further exploration to extend the learning.