The doctrine of the "Mitogaku" 水戶學 school encompasses the historiographical spirit of Tokugawa Mitsukuni's 德川光圀 (1628-1701) Dai Nihonshi 大日本史 (History of Great Japan) and the dissemination of the thought of Zhu Zhiyu 朱之瑜 (art name Shunshui 舜水, 1600-1682). It can be further described as synthesizing the interpretations of Shinto, Kokugaku (National Learning), and Confucianism as well as of the "unity of Shinto and Confucianism," the "unity of loyalty and filial piety," "loyalty to the emperor," and other morality-based ideas, establishing a system of thought on respect for the emperor with a theory of higher principles as its core. In the developmental process of the knowledge and ideology of early and later Mitogaku, Tachihara Suiken 立原翠軒 (1744-1823) played a role of inheriting the past and paving the way for the future. There are shortcomings, however, in the Japanese academic community's research on the correlation between Tachihara Suiken's knowledge system and the formation of later Mitogaku as well as the impact of the former. This paper examines the role, function, and positioning of Tachihara Suiken in the evolution of "middle" Mitogaku, aiming to clarify historical truths and fill a lacuna in its overall developmental history.
