Months before the 2016 United States presidential election, universities across the country began reporting the appearance of white nationalist flyers featuring slogans like "Let's Become Great Again" and "Protect Your Heritage" against the backdrop of white marble statues depicting figures such as Apollo and Hercules. Groups like Identity Evropa (which sponsored the flyers) oppose cultural diversity and quote classical thinkers such as Plato in support of their anti-immigration views. The traditional scholarly narrative of cultural diversity in classical Greek political thought often reinforces the perception of ancient thinkers as xenophobic, and this is particularly the case with interpretations of Plato. While scholars who study Plato reject the wholesale dismissal of his work, the vast majority tend to admit that his portrayal of foreigners is unsettling. From student protests over the teaching of canonical texts such as Plato's Republic to the use of images of classical Greek statues in white supremacist propaganda, the world of the ancient Greeks is deeply implicated in a heated contemporary debate about identity and diversity. In Plato's Caves, Rebecca LeMoine defends the bold thesis that Plato was a friend of cultural diversity, contrary to many contemporary perceptions. LeMoine shows that, across Plato's dialogues, foreigners play a role similar to that of Socrates: liberating citizens from intellectual bondage. Through close readings of four Platonic dialogues--Republic, Menexenus, Laws, and Phaedrus--LeMoine recovers Plato's unique insight into the promise, and risk, of cross-cultural engagement. Like the Socratic "gadfly" who stings the "horse" of Athens into wakefulness, foreigners can provoke citizens to self-reflection by exposing contradictions and confronting them with alternative ways of life. The painfulness of this experience explains why encounters with foreigners often give rise to tension and conflict. Yet, it also reveals why cultural diversity is an essential good. Simply put, exposure to cultural diversity helps us develop the intellectual humility we need to be good citizens and global neighbors. By illuminating Plato's epistemological argument for cultural diversity, Plato's Caves challenges readers to examine themselves and to reinvigorate their love of learning.