Cheng Yi, also known as Cheng Zhengshu, was a renowned philosopher during the Northern Song Dynasty and one of the founders of Neo-Confucianism. He, along with his brother Cheng Hao, is known as the 'Two Chengs'. Cheng Yi's thoughts had a profound impact on later generations, emphasizing that the 'Tianli' (Heaven's Principle) is the origin of all things in the universe and advocating the method of 'Learning from Things to Attain Knowledge'.