俞樾《卦气直日考》《卦气续考》所涉历法问题之辨析

Clarification and Analysis on Yu Yue's Research on the Guaqi Theory Related to Calendrical Issues

俞樾《卦气直日考》《卦气续考》所论有三点历法问题值得辨析。其一,他将四正卦值配节气之起点由“二至”“二分”改为“四立”,从而使四正卦分值四时之六节气,避免了“跨历两时”的问题。这种做法不仅于文献依据及考辨上欠妥,而且消解了四正卦初爻配合天文历法之关键节点的蕴意。其二,俞樾以阴阳爻画数阐释卦气说中六十卦的排列次序,此说有学术价值,但不能作为“改正”四正卦配值节气的证据。其三,俞樾认为卦气值日“惟京房之说为最密”,或存在观念上的误区。评价卦气值日法,需要明晰学科定位、主体立场。京房的“卦气值日法”本质上是模拟天文历法数的“逆推求合”,尽力使六十卦之赋值精切合乎天文历法之数;僧一行的《卦议》则是在天文历法的主体立场上引用易学的卦气说。

There are three calendrical issues worth analyzing in Yu Yue's(1821-1907)Guaqi zhiri kao(Textual Research on the Quaqi Theory Correlating Hexagrams and Lines with Seasonal Points and Days)and his continued research on the theory.First,he changed the starting point of the solar terms used to match the four sovereign hexagrams from“two solstices”and“two equinoxes”,to“four beginnings”,thus making the four sovereign hexagrams match the six solar terms in four seasons respectively,avoiding the problem of“crossing two seasons”.This approach is not only inadequate in terms of literature basis and textual research,but also undermines the significance of the key nodes in the correlation between the first lines of the four hexagrams and astronomical calendars.Second,Yu Yue explained the sequence of the sixty hexagrams in the theory of guaqi through using the numbers of yin and yang lines.This theory has academic value,but it cannot be used as evidence for“correcting”the matching of four sovereign hexagrams and their corresponding solar terms.Third,Yu Yue believed that there may be a misunderstanding in the concept that“only Jing Fang's theory is the most detailed”regarding using guaqi to corelate hexagrams with days.To evaluate the method of using guaqi correlating hexagrams with days,it is necessary to clarify the discipline positioning and subject position.The Jing Fang's theory essentially simulates the“reverse deduction for combination”of astronomical and calendar numbers,striving to make the assignment of the sixty hexagrams be in line with astronomical and calendrical numbers precisely;Monk Yi xing's Discussion on Hexagrams quotes the theory of guaqi in Yi scholarship from the main standpoint of astronomy and calendar.