如果天地之性才是人的本然之性，義理之性才為人性的究竟真實，則人所獨有的氣質之性是否弔詭地不能代表人性之真？吾人依此而有的氣稟形軀，是否反而成為體道成德者所當對治的欲體、所需超克的對象？這是船山對張載以迄程頤、朱熹論性架構的反省。本文要旨有三：一、釐清船山對「本然之性－氣質之性」架構的批判。二、辨析船山與橫渠對「氣質之性」所言異同。三、設若船山根本否認人有「天地之性」，他如何順通《正蒙》相關文句，維繫注解詮釋的一致性？就哲學概念與問題間的必然連結而言，他又如何處理張載原藉「天地之性」所欲解決的哲學問題？在研究步驟上，則從三項環節展開：首先，儘管張載從未使用「本然之性」，本文指出《正蒙》中的「天地之性」，即是人根源於天地的本然之性。其次，從字義方法與儒學義理上，呈現船山辨析「天地之性」一語乖謬的方法進路。依此指出，船山實以「天命之性」詮解《正蒙》「天地之性」，並主張「氣質之性仍是一本然之性」。最後，本文依據船山之概念界定，逐一檢視《正蒙注》對張載人性論提出哪些新詮？是否能前後呼應？以及船山如何獲得「非本然之性外，別有一氣質之性」的論斷。

This article include three parts: (1) to clarify Wang Chuan-shan's criticism on the framework of ＂the nature of the universe (benran) v.s. the nature of human (qizhi),＂ (2) to analyze the similarities and differences between Wang's and Zhang Zai's viewpoints of ＂the nature of human,＂ and (3) to hypothesize that if Wang originally denied that human owns ＂the nature of the heaven and earth (tiandi),＂ how could he spontaneously understand the lines in The Commentary of the Zhengmeng, and be consistent in annotation? Moreover, how did he deal with the philosophical questions regarding ＂the nature of the heaven and earth＂ that Zhang mentioned in his book in connection with philosophical concepts? Based on Wang's understanding of these concepts and definitions, this article will examine The Commentary of the Zhengmeng's new interpretations on Zhang's philosophy of the heaven and earth and the way how Wang received the main idea ＂The nature of human is separated from the nature of the universe.＂