本文站在理學工夫論的立場，重新整編相偶論與同一論的理論，相偶論是阮元(1764-1849)提出的道德理論，他主張真正的道德是在人與人之間的倫理關係中建立的，他批判理學的性理說是受佛教影響的產物，與孔孟之學不相干。本文認為相偶論需要兩次的提升。首先，在反理學的範圍內，依形氣主體的概念，相偶論不能僅從社會關係，而當從主體意識具備「內在的他者」之觀點立論，這是以戴震(1723-1777)為代表的廣義的相偶論該有的論點。接著是超越論的提升，本文從「形氣主體」以及「道體論」（亦即「先天的氣學」）的觀點，主張人的體道經驗總是在形氣主體的基礎上轉化生成的，所以即使在工夫究竟的層次，也就是進入「先天」的層次，心體中仍有最低限度的氣性（我性）存在，所以也有極隱微的心體與性體的距離。否則，「我的經驗」一詞即無法成立。即使陸王心學因預設了本體與心靈的等同，其工夫究竟層次不能不意味著「同一」的相位，但由於陸王心學沒有在氣質之性之外另立脫離氣質的義理之性，我性不可能消除，「心即理」與「心即氣」同時成立。所以其心靈終極境界的同一仍是帶著「心體」與「性體」的既相融且「相偶」的矛盾統一。一體論不離相偶論的另一個理由在理學的「性體」指向個體性存在的超越依據，既指人，也指物，且「性體」的活動義也通向道體，這是北宋理學對孟子性善義的大幅擴充。在理學敘述的性天相通之境，道體論以泛神論的模式出現，物物皆太極，此時的萬物雖不再是認識的對象，卻仍以「物如」的身分蘊於一體的境界中，不能泯滅不見。也就是在冥契為一處，仍有帶著我性的心體與「心物一如的性體」之相偶的結構。內向型的純粹一體論排斥了個體性（含人的我性）的內涵，這種「絕對同一」的「無我」之論在佛教的空性哲學處顯現得最清楚，即使大乘佛教的如來藏心論也不能脫離緣起性空義的規範。儒學沒有建立在脫離現實存在原理的氣之外的「同一論」的主張，「天命之謂性」的性體概念也沒有脫離存在依據的氣質之性的主張。本文舉牟宗三先生(1909-1995)說的理學三系人物之文獻為證，指出理學的主體如果建立在有限人性論與無限人性論的相互轉化，一體論與相偶論即不能沒有詭譎的同一。

This paper re-expounds the theory of duality (xiang’ou lun 相偶論) and the theory of unification (yiti lun 一體論) from the standpoint of the Neo-Confucian theory of self-cultivation (gongfu lun 工夫論). The theory of duality is a moral theory proposed by Ruan Yuan 阮元 (1764-1849), who considered true morality as established in the ethical relationships between human beings. He moreover regarded the doctrine of principle and the nature (xingli shuo 性理說) as a product of Buddhism, and thus it was irrelevant to Confucianism. This article argues that the theory of duality needs to be enhanced in two ways. First, in the context of anti-Neo-Confucianism, it must be aligned with the concept of the “body-qi subject;” the theory of duality cannot be based solely on social relations, but must also be rooted in the idea that the subject consciousness has an “inner other.” This viewpoint should be derived from the broader sense of the theory of duality represented by Dai Zhen 戴震 (1723-1777). The second enhancement is tied to the theory of transcendence. From the perspective of the “body-qi subject” and the daoti lun 道體論, i.e. the congenital theory of material force, this article argues that the experience of embodying dao 道 has to be transformed and generated on the basis of “body-qi subject.” In this way, even at the highest level of moral cultivation, i.e. at the level of “innate subjectivity,” there is still a minimum amount of psycho-physical nature in the mind and body. The reason why the theory of unification cannot be separated from theory of duality is that moral subjectivity in Neo-Confucianism refers to the transcending ground of individuality; that is, it refers to both persons and objects. Confucianism does not establish a “theory of identity” without the existence of qi 氣, nor does the concept of the “heaven-endowed nature” detach itself from the nature of qi as the basis of existence. If Neo-Confucianism is based on the mutual transformation of the theory of finite and infinite human nature, then the theory of unification and the theory of duality are paradoxically identical.