John Green explains the history of Buddhism and how Siddhartha Guatama, or Buddha, set the foundation for the religion. He briefly discusses Siddhartha's life as a prince and how he became Buddha. John then describes the Four Noble Truths, the essence of Buddha's teachings, and gives a glimpse into the life of monks following the religion. He touches upon how the religion spread and was particularly attractive to low-caste Hindus.