The main content of Mengzi (the Book of Mencius) is the sayings of Mencius and his disciples. Mencius proposed the virtuous humanity theory: he believed that human was born with four moral characters -- the humanity, justice, courtesy, and wisdom. Human would lose the moral characters if he didn't maintain or develop them by practice. Hereby, he demanded people to pay attention to inner cultivation.

Mencius advocated benevolent policy and kingcraft. Benevolent policy meant reducing penalty and taxes. He thought that tyranny was the fundamental cause of perdition.

Mencius' democratic idea suggesting demos are nobler than monarch and is of great value. He thought that the emperor must attach importance to the interest of ministers and common people, ministers should dissuade their emperor from blundering. Everyone had the right to scepter other solon if the emperor excluded suggestions, and even to be tyrannicides if the emperor was a tyrant.

Mencius opposed arbitrariness, and proposed to conquer other country by policy of benevolence and kingcraft instead of war but to conquer opposite country by morale. 

Mencius inherited and developed the theory and ideology of Confucius. His status and influence to the later generations was just inferior to that of Confucius. In the Northern Song Dynasty (960-1127) Mengzi was ranked as Confucian classics and its status was elevated; in the Northern Song Dynasty (1127-1279) Zhu Xi compiled Mengzi and Lunyu (The Analects), Daxue (The Greater Learning) and Zhongyong (The Center of Harmony) into The Four Books. From the Song Dynasty (960-1279) to the Ming Dynasty (1368-1644), The Four Books became an indispensable reading for intellectuals.