And because of the influence of the Neo-Confucians, especially their focus on belief in order and logic of the universe, it's no coincidence that the Sung Dynasty saw some of the major technological advancements, not just of China, but of the world, advancements that really put China at the technological forefront. Remember, Europe at this time is in the Middle Ages. The Middle East is under the Golden Age of Islam, but it's really the Chinese who are pushing the envelope here. Now just get a flavor of some of Zhu Zi's writing. Original mind is principle as derived from Tai Chi in itself, unmoved and perfectly good, while physical nature on the other hand is principle mixed with material force, qi. It is the aroused state involving both good and evil. The two natures, however, are always interfused, one the substance and the other function.