The theory of good nature is a theory of human nature put forward by Mencius in the Warring States Period. Mencius believes that good nature can be verified by the universal psychological activities that everyone has. Since this kind of psychological activity is universal, the goodness of nature is based on human nature, which Mencius called "conscience" and "goodness".

The theory of evil nature was advocated by Xunzi at the end of the Warring States Period. The essence of human nature mentioned by Xunzi is just the natural nature of "primitive materials" which does not care about good and evil. It has both the possibility of turning into evil and the opportunity of developing into good.

The theory of evil in human nature emphasizes the necessity of moral education, while the theory of good in human nature focuses on the consciousness of moral cultivation, which are both opposite and complementary, and have a great influence on the theory of human nature in later generations.