"Platonists believe that there is a universal truth underlying all of mathematics. Formalists believe all of mathematics can be defined by a set of predefined rules. Ever wonder about the deeper significance of these two critical mathematical philosophies? Using thought experiments like the Allegory of the Cave and the Barber's Paradox, the great mathematics popularizer and author of Is God a Mathematician?, Mario Livio, untangles these two didactic ways of viewing the world and the very nature of human knowledge."