The Four Books
During the Song Dynasty, Zhu Xi's teachings were considered to be unorthodox. Rather than focusing on the "I Ching" like other Neo-Confucians, he chose to emphasize the Four Books: the "Great Learning", the "Doctrine of the Mean", the "Analects of Confucius", and the "Mencius" as the core curriculum for aspiring scholar officials. For all these classics he wrote extensive commentaries that were not widely recognized in his time; however, they later became accepted as the standard commentaries. The Four Books served as the basis of civil service examinations up until 1905, and education in the classics often began with Zhu Xi's commentaries as the cornerstone for understanding them.