Interpreting Buddhism, Confucianism and Taoism as well as comparing Chinese and western philosophies throughout his life, Mou Tsung-san wrote Physical Nature and Speculative Reason, Substance of Mind and Substance of Nature and Buddha Nature and Prajna and then edited From Lu Xiang-shan to Liu Ji-Shan and The Theory of the Highest Good in his late years. Mou's discussion of Liu Ji-shan in From Lu Xiang-Shan to Liu Ji-shan is special in two senses. First, Mou's achievement in the interpretation of Confucianism, Buddhism and Taoism is embodied in his interpretation of Liu Ji-Shan; therefore, we get to see the overview of his philosophical thinking. Second, his interpretation of Liu Ji-Shan suggests two themes, that is, ”the manifestation of nature through mind” and ”returning from exoteric to esoteric teachings.” The former theme is interwoven with the approach of the doctrine of mind and therefore superfluous. On the one hand, it is deliberately distinct from but inevitably similar to the doctrine of mind; on the other hand, it is nothing but a doctrine that's different from Cheng and Chu's theories about mind and nature. As for the latter, it is indeed an overview of Liu's practical theory and significantly different from Wang Yang-ming's practical theory in terms of focuses, which is actually the difference between simplicity and complexity.