Confucius. Buddha. Jesus. Muhammad. Four extraordinary sages who influenced world civilization more deeply than any other human beings in history. As just one measure of their importance, current rankings of the most influential people in history consistently put them at or near the top of the list. Four centuries after the rise of the scientific worldview, their influence in human affairs continues to be fundamental, underscoring issues ranging from questions of ethics and justice to religious and political conflicts to other issues that dominate today's headlines.