船山從學術之蔽反省，認為亡國的關鍵在王學，尤以「無善無惡圓融事理」之說為最。船山意圖矯轉王學末流頹風，必從心學之根源處下手。船山回過頭重新審視前儒所輕之「氣」，重視經驗實在之理，曰「氣即理」。亦別於前儒路數，從承認人欲出發談天下之公理。處理的問題主要有二：一是天理人欲對立的問題；二是人欲的公私問題。由前者，船山對程朱、王學，皆有所彈核，因為「存天理去人欲」於外王理想實現的可能性相對微弱。由後者，分辦人欲的公私問題，使人合理的自我實踐動力不在個體，而在全體，是則，個體欲望的實現同時也是全體福祉的完成，外王功業可由個體的努力而建立。是以嚴詞批評李贄。與前儒最大的不同是，加山之根本思想，在肯定即「氣」即理之「性」，而暢發「氣亦善」之義。不甘於只在心上做工夫。而是要問心體之創造落實在歷史文化社會人生之事上而即事以言者，故曰「人欲之各得，即天理之大同」。

Chuan-shan reviewed ”Chi” neglected by the former Confucianists and valued the principle of experience. It means ”Chi is Li”. Different from the former Confucianists, he discussed general truth of the world by acknowledgment of human desire. He mainly concerned the following issues: one is conflict between justice of nature and human desire and the other is public and private issues of human desire. Regarding the former, Chuan-shan impeached Chen-Chu, Theory of Wang Yang-ming since it is less likely to apply ”keeping justice of nature and eliminating human desire” to external implementation of benevolent rule. As to the latter, Chuan-shan explored private and public issues of human desire. Thus, the drive of individuals' reasonable self-realization is not based on individuals, but the whole. Fulfillment of individual desire is the accomplishment of welfare of the whole. External implementation of benevolent rule can be constructed by individuals' efforts. Thus, Chuan-shan criticized Li Zhi with severe words. Different from the former Confucianists the most IS that Chuan-shan's essential thought is the affirmation of nature of ”Chi” and Li and fulfillment of justice of ”Chi is righteousness”. Instead of mere efforts on mind, creation of mind ware is applied to history, culture, society and human life as the principle of behavior. Thus, ”individual acquisition of human desire is unification of justice of nature”.