Imperialism (sonnoron) is the idea of valuing the emperor above all else. Originally it stemmed from Confucianism in China and was introduced into Japan after undergoing a certain degree of transformation.
In imperialism, respect for the 'emperor' who is said to govern his people with virtue, justice and benevolence is advocated, over respect for 'supremacy' or a supreme ruler who governs his people with military force (military rule). In China, since the rulers of the ancient Chou kingdom were taken as the ideal model for the emperor, the word 'king' was used instead of emperor. At the time when imperialism was introduced into Japan in the Edo Period (the period during which the Tokugawa shogunate ruled Japan from 1603 to 1867), the tenno (emperor) was advocated as the 'king' and the shogun of the Tokugawa shogunate was the 'military ruler'; despite this, sometimes the Chinese character meaning emperor was used instead of 'king', based on assumptions of superiority, that the emperor was more than a mere 'king'.
In the shogunate system, the Imperial Court had restrictions put on it by the shogunate, but it was nominally situated at the top of the order of authority and the religious system. When confusion over reform of the shogunate system and political chaos due to tension with foreign countries occurred, the Tokugawa shogunate tried to make use of the authority of the Imperial Court for the maintenance of political order, insisting that its political power was entrusted by the Imperial Court, and through this the authority of the Imperial Court was restored.
In the middle of the Edo Period, the study of the Japanese classics (National Learning) became popular, and the shinto religion in addition to such famous historical works as the Records of Ancient Matters and Chronicles of Japan were increasingly studied, and the study of Japanese classics spread among the intellectual class including samurai warriors and rich farmers. In addition, the restoration of emperors' tombs and a tendency to connect the ancestors of feudal clans to the imperial line arose. At the end of the Edo Period, imperialism became more absolute as nationalism was advocated in the Hirata Japanese classics and in Mitogaku, a school of Japanese historical and Shinto studies that arose in the Mito domain, and imperialism also developed into a movement to abolish Buddhism. When the Tokugawa shogunate ended its policy of isolation and concluded treaties with foreign countries, opening Japan to the outside world, imperialism was fused with the principle of excluding foreigners, and grew into an anti-foreign imperialism; this became a conduit for criticism of shogunate policy and for the anti-shogunate movement, and exerted an influence on national polity theory and State Shinto.
The Tokugawa shogunate adopted the teachings of Zhu Xi (a Chinese philosopher of the twelfth century) as the principle of controlling people and Confucian philosophy took hold. However, the Tokugawa shogunate originally came to power at the end of years of battles among military families and the shogunate corresponded to the 'military government' which was contrary to 'righteous government', therefore the logic for justifying the Tokugawa shogunate was filled with contradiction from the beginning. In China, the model for Confucianism and the object of admiration, the Ming dynasty went to ruin and the country came to be controlled by the Ching dynasty; China was said to have been reduced to 'a country of beasts' and no longer acted as a standard to emulate.
Therefore, Soko YAMAGA said that the orthodox Confucianism rooted in Japan and concluded 'Japan was China.'
Moreover, the establishment of Confucianist thought in Japan meant the establishment of a China-centered view of the world in Japan, which had an influence upon emperor-centered historiography in later times and became the foundation for a Japanese style China-centered view of the world. In Confucianism, whether to allow the expulsion of a disqualified monarch had been a difficult problem to deal with, but the Tokugawa Shogunate adopted a position taken from the standpoint of Mencius (a Chinese thinker in the fourth century BC) concerning the teachings of Zhu Xi, and approved of the Tang-Wu revolution (the expulsions of disqualified monarchs by King Tang and King Wu) and the revolution (change of dynasty) decreed by Heaven (when the incumbent emperor is found lacking in moral virtue). The adoption of such a principle would mean that a shogun would be able to expel an emperor; consequently the Kimon school founded by Ansai YAMAZAKI took a position opposed to the expulsion of a disqualified monarch and transformed Zhu Xi's teachings from a pro-establishment ideology to one that was anti-establishment. Furthermore, conventional Chinese thoughts were Japanized in the same way, and united with the doctrine of excluding foreigners, developing into a radical political position criticical of the shogunate and its domain system, and as such, this became a driving force for the Meiji Restoration.