【摘要】 宋元以降，道教学者广泛论及先天和后天，却并未对其进行严格界定，相关论述亦较为笼统。李西月基于前人对先天和后天的理解，将宇宙的生成次第解释为先出于天者、先原于天者、后天（包括后天中之先天和后天两个层面）等阶段，并强调内丹学由后天所返还之先天合前二义而兼有之。与之相应，丹有二品，即结丹和还丹，其炼养次第为结丹、七返还丹、九转大还丹；药有二类，即内药和外药，其用药次第为始则取外药以制内药，继则由内药以修外药，终则食外药以合内药。李氏的先后天思想不是对前代先后天思想的简单综合和总结，而是在其基础上的一次创新性发展，透显着他对宇宙生命的独到认知，具有重要的学术价值和理论意义。更多还原

【Abstract】 Since the Song(960-1279) and Yuan(1271-1368) dynasties, Taoist scholars have extensively discussed the concepts of Former Heaven and Later Heaven, but have not strictly defined them, and the related discussions are also comparatively vague.Based on previous understandings of Former Heaven and Later Heaven, Li Xiyue(1806-1856) explained the generation order of the universe as the stages of being born in Former Heaven, originating in Former Heaven, and Later Heaven(including both Former Heaven in Later Heaven and Later Heaven two levels), and emphasized that the Former Heaven based on the returning from Later Heaven in internal alchemy refinery combines the above two meanings of Former Heaven. Correspondingly, there are two layers of alchemical achievements, namely jiedan(establishment of alchemy) and huandan(sublimation of alchemy), with the refinement and cultivation processes jiedan, huandan after seven returns, and supreme huandan. There are two types of medicine, namely internal medicine and external medicine. The order of using the medicine is: at first take external medicine to restrain internal medicine, then use internal medicine to refine external medicine, and finally eat external medicine to combine internal medicine. Li’s thought of Former Heaven and Later Heaven is not a simple synthesis and summary of the previous thought, but an innovative development based on it, which highlights his unique understanding of the universe and life, and has important academic value and theoretical significance.更多还原