The issue of human nature is an eternal theme in the history of human thought. Mencius’ proposition of the original goodness of human nature was proposed over 2,300 years ago and has sparked countless debates throughout history. It has not only impacted East Asian countries such as Japan, Korea, and Vietnam but also had a vast influence on Western academic circles in the 20th century.Building upon a comprehensive study of various viewpoints on Mencius’ theory of the original goodness of human nature from China, Japan, Korea (South Korea), and Western countries, this book offers a new interpretation of this theory of Mencius’. It provides new insights into understanding the concept of human nature as perceived by the ancients, how the theory of original goodness of human nature can be viewed from the perspective of the law of growth, and the main issues and debates surrounding Western theories of human nature over the past two millennia. Many of these viewpoints were not discussed in the academic circle and are of paramount value to the deepening and reevaluation of Mencius’ theory of the original goodness of human nature.