This book was written by Gan Long, Mei Gucheng, Yun Lu and He Guozong.
Kong Xuan is an easy word to learn. The chapter on Metaphysics in Shen Shi's Metaphysics explains the meaning of Metaphysics as follows: "It is the word Metaphysics, which means that one to nine are natural, and one to nine are uncertain, and there are complicated understandings, so the word Metaphysics is used instead." It means: Kong Xuan stands for the number 1 to 9, because 1 to 9 is not arranged according to the regulations, but there are many changes, so it is replaced by Kong Xuan. Kong Xuan is mainly used for geomantic omen, so there is a school of geomantic omen called Kong Xuan Geomantic omen.