The Neo-Confucian tradition of the Song Dynasty not only regarded the issue of good and evil as an ethical concern related to human affairs but also sought to explore the origins and unity of good and evil at the cosmological level： how the foundation of cosmic order could simultaneously be the source of both good and evil. In relation to the theory of human nature， the Song Dynasty Neo-Confucian tradition proposed three typical responses. The approach represented by Hu Hong 胡宏 regarded human nature as a fundamental principle transcending the distinction between good and evil， with good and evil being the effects or outcomes produced by nature as a capacity. Zhang Zai 张载 interpreted the Way （Dao） as the continuity of transformative activities and human nature as centeredness， regarding centeredness as the highest good—a state of harmony between good and evil. The Cheng-Zhu 程朱 lineage systematically reflected on the previous two lines of thought and argued that the essence of human nature is inherently good， with evil being a deviation or departure from good. This perspective upheld a “monism of good” while simultaneously avoiding anthropomorphic interpretations. The Cheng-Zhu approach shows that only by adhering to the original and inherent goodness of the foundation of cosmic order can the order of the ethical world be truly defended and a slide into historicism be avoided. Regarding evil as a deviation represents a full consideration of the complexity of the ethical world and its tension with the foundation of ultimate goodness.