Cheng Yi (程頤; 1033–1107), also known as Yichuan (伊川), was a Chinese philosopher, politician, and educator of the Song dynasty. He was a key figure in the development of Neo-Confucianism. Along with his older brother, Cheng Hao (程顥), he is considered one of the "Two Cheng Brothers" (二程).
Cheng Yi focused on li (理, principle or pattern) as the fundamental organizing principle of the universe and of human morality. He believed that li is inherent in all things and that understanding li is essential for self-cultivation and good governance. His philosophy emphasized the investigation of things (格物, gewu) to discover the underlying principles. He saw this investigation not as a purely empirical exercise but as a process of moral self-improvement, allowing individuals to align themselves with the natural order.
Unlike his brother who emphasized the importance of intuition and the spontaneous expression of li, Cheng Yi stressed the need for disciplined study and rigorous moral practice. He advocated for a systematic approach to self-cultivation, including the study of classical texts, careful reflection, and diligent effort to correct one's behavior. This emphasis on practice and disciplined learning became a defining characteristic of the Cheng-Zhu school of Neo-Confucianism, which later became the orthodox state ideology.
Cheng Yi held several government positions throughout his life, often serving as a lecturer at the imperial court. He was known for his outspokenness and willingness to criticize corrupt officials, even at personal risk. His political views were rooted in his Confucian belief in the importance of virtuous leadership and the promotion of social harmony.
His writings, including The Collected Writings of the Two Cheng Brothers (二程遺書) and Explanation of the Book of Changes (易傳), significantly influenced later generations of Confucian scholars and shaped the intellectual landscape of China. His teachings on li, self-cultivation, and the importance of moral principle continue to be studied and debated today.