牟宗三先生曾依本體的活動與否，將理學歸為「即存有即活動」、「存有而不活動」二種型態，朱子被判屬後者。拙文以為，朱子理氣論的設計，當源於對「惡」經驗事實之正視。只要是一元本體論，基本上都會面對「善惡同體」的理論困難。為了維護理的純粹至善，又要對惡的由來有合理解釋，朱子乃有「理掛搭在氣上」不活動的情形。理為至善，惡為傍出，所以朱子斥「性無善惡」論點為非。不過，這套理論除了解釋心性善惡之外，同時也是用以說明一切現象存在的本體論，這就使得問題有些複雜。依朱子理論，現象的發生，來自理氣的結合。不同於印度數論派哲學「絕對的不活動」型態，朱子的理仍參與、內寓於現象之中。依「天地萬物莫不有理」的說法，合理推論，惡之事物也應有惡之共相，這就有導致「事物善惡皆有理」的可能。同時，朱子論理氣另有「相袞」之說，理氣的關係就不是掛搭，而是「天地之性在氣質之中穿過」的型態。依此型態，理就未必全然不活動，只不過是透過氣質來作用。依朱子「性體情用」的說法，情有善惡，逆推回去，也就不無性具善惡、性無善惡的可能。藉《大乘起信論》為比對，同一本體做為善惡現象共同根源，則本體的不變之性，當不能以現象善惡名之，這就有超越善惡、非善非惡的可能性，但這結果恰為朱子所極力反對者。

Mou Zong-San has ever divided the Neo-confucianism into two styles: existing and active, as well as existing but not active. Classified to be the latter, Zhuzi’s theory is designed under the motive for the empirical facts of evil. Generally speaking, Monism inevitably encounters the problem of virtue and vice caused by the same substance. To keep the Li (principle) purely good in explanation of source of evil, Zhuzi has the statement that the Li (principle) doesn’t act, only attaching to the Qi(material force). With Li as purely good, so Zhuzi disagrees about the nature to be neither good nor evil. According to Zhuzi’s theory, phenomena are organized by both Li and Qi. Consequently, the vice is constituted in the form of evil. Furthermore, Zhuzi also defined phenomena as Li permeating qi, which means Li may act through Qi. Therefore, the possibility of both virtue and vice in the substance may be inferred from Li, which represents perfection of Li would be transcendental rather than ethical.