 The Song Neo-Confucian philosophers, finding a certain purity in the originality of the ancient classical texts, wrote commentaries on them. The most influential of these philosophers was Zhu Xi, whose synthesis of Confucian thought and Buddhist, Taoist, and other ideas became the official imperial ideology from late Song times to the late 19th century. The basis of his teaching was influenced by the Cheng brothers, but he greatly extended their teachings, forming the core of Neo-Confucianism. This included emphasis on the Four Books: the Analects, Mencius, Doctrine of the Mean, and the Great Learning (the latter two being chapters in the ancient Book of Rites). His viewpoint was that improvement of the world began with improvement of the mind, as outlined in the Great Learning. His approach to Confucianism was shunned by his contemporaries, as his writings were forbidden to be cited by students taking the Imperial Examinations. However, Emperor Lizong of Song found his writing to be intriguing, reversing the policy against him, and making it a requirement for students to study his commentaries on the Four Books.
