The Book of Mencius is a foundational text of Confucian philosophy, attributed to Mencius, a Chinese philosopher who lived around 372-289 BCE. This text elaborates on Confucian ideals such as humaneness, righteousness, and the importance of moral governance, serving as a commentary on the teachings of Confucius and further developing his ideas. It emphasizes the inherent goodness of human nature and outlines the role of rulers in cultivating virtue and moral behavior within their subjects.