船山哲學在明清之際各家思想中最為突出；對於明代以來漸受重視的氣論思想，他非常深入地建構起以氣為基礎的存在論範疇、天道觀，即「氣本論」立場的宇宙本體論思想。船山對於「天道」之真實存在與「人道」所理解的天道觀，加以區別其間不同。關於天道之真實自存，船山認為應從〈繫辭〉曰「天地之大德曰生」的高度言，是指「天地無心而成化」之「天以陰陽五行化生萬物」，故天道不限於人道所理解的「唯人為有仁義禮之必脩」，人道只是天道的一種展開形式而已，不足以盡「天道之本然」。由是，船山立基在張載「有無混一之常」之強調氣有聚散顯隱不同、但無所謂「有無」的氣論思想上，而從「氣」為天道本體的哲學高度，建立起涵蓋論氣、理、氣之理、氣之變合運動規律、以氣論性的人性論之完整思想體系。是故船山哲學的歷史作用，在於他在理學走過了程朱主流強調「理本論」與陽明心學主張「心本論」之高峰發展和理論建構之後，轉從重氣的角度，成完了儒學思想從理本→心本→氣本的全幅開發歷程，成為我國明清之際最具哲學深度的理論建設。

Chuanshang philosophy was the most significant among all schools of thoughts in Ming and Qing Dynasties. On the gradually emphasized qi-based theory from Ming Dynasty, he profoundly established the scope of existence theory and viewpoints on heavenly laws, i.e., qi-based theory in the thoughts of universe ontology. Chuanshang distinguishes the differences between real existence of heavenly laws and heavenly laws understood by human laws. For the real existence of heavenly laws, Chuanshang believed to start from birth as the great virtue of the heaven and earth, meaning the heaven gave birth to all objects with ying, yang and five elements in the heaven and earth are formed unwittingly. Therefore, the heavenly laws are not limited to only humans have benevolence, righteousness and courtesy. Human laws are just an extension of heavenly laws, failing to fulfill the foundation of the heavenly laws. As a result, based on the philosophical height of qi as the subjectivity of heavenly laws, Chuanshang established the complete thoughts covering qi, reasons of qi and movement rules, and exploring nature with qi-based theory, being the most profound theory construction in philosophy between Ming and Qing Dynasties.