本文對於船山詮釋《孟子》中「盡其心者」一章作一解說，此章孟子談到盡心、知性、知天，其中的心、性、天是全章的重要概念。然而朱子在詮釋此章的心、性、天時，用了二個學者的話來解說，一者程子，程子之言是「心、性、天，一理也。」另一人乃張載，朱子用張子「由太虛有天之名，由氣化有道之名」等語以詮釋心、性、天。而船山面對此二人的見解，想於其中比較出詮釋的高低，而歸旨於張載的氣化天道思想，而不取程子的心性天根源於一理的看法。在此看出船山的重氣的義理，亦可視為船山以氣學思想，用以取代程朱的理學思想。又，船山面對朱子以「格物」之說解「知性」，認為語甚奇特，卻不反對，理由在於船山所理解的格物，是不離倫物、不離於氣化的意思，他認為如此可以區別開佛老之離倫物。故在此可以看出船山如何以重氣思想，於程朱的理學之外，重新詮釋孟子。

This study contains an explication of Chuanshan's interpretation of ＂Mencius. Jing Qi Xin Zhe Zhang＂ (＂Chapter on Those True to the Heart＂), a chapter in which Mencius dwells upon being true to the heart, knowing human nature, and knowing about ＂Tien＂ (the heavens). The concepts of heart, human nature and the heavens are vital to the chapter. However, in his interpretation, Chu Hsi quoted the explications of two scholars on heart, human nature and the heavens to convey his own interpretations, one of which was Chen Tse, who held that ＂heart, human nature, and the heavens are of one origin.＂ The other explication came from Chang Tsai, whom Chu Hsi quoted saying ＂the original emptiness is the name of the heavens, spiritualization is the name of Tao＂ in order to interpret the heart, human nature and the heavens.In Wang's attempt to conjoin the interpretations of these two scholars, he placed heavier emphasis on one rather than the other, namely, he took after Chang Tsai's interpretation of the spiritualization of Tien and Tao, and discarded Chen Tse's opinion that the heart, human nature, and the heavens are of one origin. It was evident that Wang relied more heavily on the theory of Chi, and it may also be said that Wang employed the thought of Chi to replace the theoretical thought advocated by Chen and Chu. Moreover, Wang considered Chu Hsi's interpretation of ＂knowing the ways of the world＂ as ＂knowing human nature＂ eccentric, but did not express dissent, because Wang's understanding of ＂knowing the ways of the world＂ is not to detach oneself from morals and material things, and not to detach oneself from spiritualization. It was his opinion that, in this way, Mencius' thought could be differentiated from the detachment theories that are considered as more appropriate to Buddhist thought and the thought of Laozi. The emphasis on thought of Chi was Wang's contribution to the interpretation of Mencius beyond the teachings of Chen and Chu.