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.

John Green discusses how Jesus spread Christianity using his public image of being considered the Messiah. He also mentions a couple of historical reasons for Christianity becoming a world religion: The Jews opening up their religion to non-Jews, and Saul of Tarsus (Paul the Apostle) actively spreading Christianity throughout the Mediterranean.

Christianity, a religion based on the teachings of Jesus Christ, has about two billion followers. Learn about the story of Jesus Christ, where the Christian faith originated, and how it grew to become the largest religion on the planet.

John Green discusses early Islamic history and some of the beliefs of followers of the religion. Like Christianity and Judaism, Islam is a monotheistic religion and has religious texts, most notably the Quran. John some of the themes of the religion: strict monotheism and the importance in taking care of others that are less fortunate. Also, he covers the Five Pillars of Islam: Shahada, Salat, Sawm, Zakat, and Hajj.

John Green explains the history of Judaism in Rome. He mentions that the Jews were tribal people of Judea, a Roman Province, and covers some of the characteristics and beliefs of their religion, such as monotheism and the Covenant. He also details traits about the Jews' God, such as singularity and transcendence.