This article is concerned chiefly with comparative Confucianism, specifically a comparison of two revisionists of the Chu-tzu school-Lo Ch’in-shun羅欽順of the Ming dynasty and Kabara Ekiken貝原益軒of the Edo ear of Japan. Lo considered himself a scholar of the Chu-tzu school, but the serverely criticized its division of li理and ch’i氣in his representative work Kun-chih-chi困知記. Kaibra, who was inspired by Lo, criticized the theory of the transcendental goodness of human nature (性善論)and the division of li and ch’I sternly in his prominent work Taikiroku大疑錄. Although Lo influenced Kaibra, they had distinct philosophies. Kaibara gave up the search for transcendence and the mode of “nature is reason” (性即理) in Taikiroku. With his hermeneutic turn, Kaibara transformed the essence of Neo-Confuciansim: the key words of t’ai-chi大極, li, and tao道totally lost their transcendental meanings and became a prescription or attribute of ch’i. Lo Chi’in-shum, on the contrary, firmly maintained the transcendental dimension. Despite replacing the division of li and ch’i with the theory of the identity of the two or the “principle with many manifestations” (理一分殊), he emphasized the paradox ical ontological identity of li and ch’i. Lo remained revisionstic within the Ch’eng Chu school; Kaibara betrayed it and moved towards a naturalistic “Ch’iism” (唯氣論), that is, a refined materialism. Through a comparison of these two representative Confucians, I reveal that the theory of ch’i contained two aspects which resulted in two different philosophical systems in modern Confucian thought. The example of Lo Ch’in-shun and Kaibara Ekiken is not unique, but rather universal in late East Asian Confucian thought.