A foundational master of Northern Song Luo Learning, known as Master Yichuan. He established "Heavenly Principle" as the supreme objective metaphysical ontology of the cosmos and proposed the classic thesis that "nature is Principle," advocating the rational and cumulative path of "investigating things to extend knowledge"—examining the principles of external things one by one until achieving "sudden comprehensive penetration." His rigorous rationalist methodology became the core route of the Cheng-Zhu school of Neo-Confucianism.
Cheng Yi, courtesy name Zhengshu, a native of Luoyang, Henan. He and his brother Cheng Hao both studied under Zhou Dunyi and also attended the Imperial Academy, where his essay "What Learning Did Yan Hui Pursue?" stunned the capital. Hu Yuan, amazed at his talent, broke convention to grant him an academic position. His character was stern and upright, rarely smiling, and he conducted himself as a teacher. During the reign of Emperor Zhezong, recommended by Sima Guang and others, he was appointed lecturer at the Chongzheng Hall, teaching the young Emperor Zhezong. Known for his severity, he often remonstrated with a grave countenance, causing dissatisfaction at court. Later implicated in the factional struggles between reformers and conservatives, he was repeatedly demoted, and in his later years was placed under surveillance in Fuzhou, yet he continued writing under adversity. His scholarship emphasized rational discipline and logical deduction, in stark contrast to his brother's holistic intuition. Yet together they laid the foundation of the Luo school. Zhu Xi inherited his doctrine of "investigating things to extend knowledge" and achieved the grand synthesis; the two Chengs were later called "Cheng-Zhu," and his rationalist spirit profoundly shaped the East Asian academic tradition for eight hundred years.
Cheng Yi takes "heavenly principle" as the objective ontological ground and moral imperative of the cosmos: "principle" exists prior to things and is the ultimate ground of why things are as they are. "Nature is principle"—the essence of human nature is heavenly principle as present in humans; therefore human nature is fundamentally good, and evil arises from the bias and obscuration of physical endowment. Methodologically, he insists on "investigating things to extend knowledge" (ge wu zhi zhi): "Today investigate one thing, tomorrow investigate another; through accumulated practice, one suddenly breaks through to comprehensive understanding." Through gradually investigating the principles of external things, one eventually achieves "sudden comprehensive penetration"—the inner and outer, the subtle and the gross, all become clear, and the whole of one's mind's capacities become fully manifest. His epistemology combines experiential accumulation with intuitive breakthrough—a dual structure. In cultivation theory, he emphasizes "nourishing through reverence; advancing through knowledge": preserving the mind-nature with a grave and reverent attitude.
"Investigate things to extend knowledge. Today investigate one thing, tomorrow another; through accumulated practice, one suddenly breaks through to comprehensive understanding. Nature is principle. — Recorded Sayings of the Two Chengs"
Cheng Yi's outward, step-by-step investigation of things to illuminate universal principles (gewu)—how is this analogous to Bacon's scientific inductive method in their empiricist-rationalist epistemological attitude?
Cheng Yi's "investigating things to extend knowledge" and Aristotle's empirical induction both begin from particular things and accumulate cognition, gradually ascending to the rational grasp of universal principles.
Can universal truth be reached through the accumulation of particular investigations? Do the empiricist-rationalist methods of Cheng Yi and Aristotle represent parallel discoveries of the same epistemological truth?
Cheng Yi's "principle" is an objective heavenly principle existing in things; Kant's "categories" are subjective a priori forms that impose order on experience. The two are diametrically opposed in the subject-object placement of principle.
Is the order of the world in the world itself or imposed by the mind? Do the opposite positions of Cheng Yi and Kant on the locus of principle represent complementary truths or fundamental incompatibility?
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