災異 漢學 乾嘉學派 不書即位 桓無王 象數 旁通 之正 所存者神 孝 孝治 Disaster Classical studies in Han dynasty Philological studies in Qianlong and Jiaqing Thrones Not writing in throne No king in Huan Throne Image and numenology Side connections To be just Spirit-preserving Filial piety Governing by filial piety