First of all, it preserves many ancient documents that have been lost.
We know that with the development of science, astrology has been gradually abandoned by people, and correspondingly, a large number of astrological works have been lost, which has brought great inconvenience to future generations. However, Yi Sizhan was compiled by many works of astrology in the previous generation, which preserved many valuable historical materials of astrology for us. For example, in the Eastern Han Dynasty, there were very few historical materials about the sea stars. When astronomer Zhang Heng wrote Ling County, he described the number of Chinese and foreign officials in detail, and then mentioned that the proportion of sea people did not exist. Among the ancient books cited in Yi Sizhan, there is a book called Zhan in the Sea, which is naturally valuable. For another example, most of the Wei books that prevailed in the Han Dynasty were lost after the Sui Dynasty strictly banned them, but many contents of the Five Books of Han Jing Wei were preserved in Yi Si Zhan. The quotation of Shi, Gan and Wu Xian in Yi Sizhan is also beneficial for future generations to study these astronomers in the Warring States period.
It should be pointed out that Yi Sizhan is not as detailed as the later Kaiyuan Zhan Jing in terms of data preservation, but it was written before Kaiyuan Zhan Jing and has the function of connecting the past with the future. Moreover, Zhan Jing in Kaiyuan did not choose to abandon other scholars when collecting ancient books before, which played a great role in preserving old materials, but it was inevitably trivial. In contrast, Li's "B has occupied" is still slightly better. The deficiency of Station 14 is that it doesn't clearly point out the origin of Wen Zhan in many places. Li explained: It is no longer in the name of the theory of predecessors, so I dare to hide it without revealing it, and because I am young, I am used to reciting it, and I am confused before and after, fearing that I will lose my true colors. Although his practice is excusable, it brings inconvenience to future generations. Fortunately, Kaiyuan Zhan Jing made up for this defect. For modern people, as long as the two books are read together, we can have a general grasp of the development of astrology in China before the Tang Dynasty.
In addition, A Touch helps us to fully understand Li. Li was an outstanding astronomer and famous astrologer in the Tang Dynasty. Traditionally, people's understanding of his astrology theory is mainly reflected in the records of the old and new versions of Tang Shu and other books. The understanding gained by doing so is easy to be one-sided. For example, in the Book of Old Tang Dynasty, it is said that every time he occupies good or bad luck, it is consistent with the deed. At that time, the artist suspected that he had other slavery, but it could not be measured for learning reasons. Li is famous for waiting for the efficacy of astrology, but he himself does not advocate the special pursuit of the efficacy of astrology in Yi Sizhan. He pointed out that if heaven is far away, the change is uneven and the reason is unpredictable, so we should feel the same? Zi Shen, long-term care of the stove, occupation or not, the situation has gone down, how to say it. If you talk a lot, you are not respected by me. In other words, nature is complicated, and it is difficult for astrologers to explain it accurately. What astrologers want to pursue should not go into details, but should be expedient measures, consider the way of governing the country, examine the right and wrong of personnel, and establish doctrines based on Shinto. It can be seen that he promoted astrology as an auxiliary means. For another example, when he discouraged Emperor Taizong from killing innocent people, he said, "God forbid." However, Xiu De emphasized in the third volume of Yi Si Zhan that Xiu De should be punished for sudden changes. These two views are essentially contradictory. If you don't read Yi Si Zhan, it is difficult to understand this aspect of Li Thought. Moreover, what Yi Sizhan said accords with the basic principles of ancient astrology in China. Astrology emphasizes understanding the so-called heavenly heart and providence by observing astrology, and then Xiu De will use it to make God take back his unfavorable fate. Without this article, the soil on which astrology depends would not exist. Through the discussion of Yi Sizhan, we have a new understanding of the old and new editions of Tang Shu.