朱子的宇宙論中，理是一切具體存有超越根據，既然萬物皆此超越之理的決定，何以世上有遺理的惡事發生？此是朱子宇宙論中的一個難題，朱子本人亦意識到這一問題，然而其回應卻是令人失望的。筆者的看法是：朱子的宇宙論在這一點上的確可以自圓其說（不管朱子本人是否意識得到）。 　　朱子所謂的氣質之性可細分為「氣質之性Ａ」及「氣質之性Ｂ」，而正是氣質之性Ｂ使人有一切的生理及心理上的欲求。這些欲求本身並無所謂善惡，然而人的心卻可以順從天理而為道心，亦可單被氣質之性Ｂ所決定而為人心。若是後者，人欲便有過與不及之情況出現，這便是惡。故此惡的可能性是在天理決定宇宙的生化過程中三個不同層次的具體內在化所引至的自我限制下產生的，而惡的具體產生卻是人心的自由決定所的。

　　　　　“Li” is the transcendent basis in Zhu Xi's cosmology. The myriad of creatures are then accordingly determined by this principle of “Li”. Where, then, is there any room for an occurrence of evil? This is a sticking point in Zhu Xi's cosmology. Zhu Xi himself was aware of the problem of evil in his philosophy, but his treatment of the problem was disappointing. My own viewpoint is that a more comprehensive analysis of this problem would have given Zhu Xi's philosophy completeness. (Whether or not Zhu Xi himself would have thought so.) Zhu Xi's “Qi Zhi Zhi Xing” can be further divided into “Qi Zhi Zhi Xing A” and “Qi Zhi Zhi Xing B”. It is within “Qi Zhi Zhi Xing B” that “Li” is born and human beings find the desires of the mind. These desires in themselves are neither good nor evil. A person can choose either to follow the “Li” of heaven and make it the way of the mind or just allow “Qi Zhi Zhi Xing B” to dictate the mind's path. It is in choosing the latter that the possibility of evil arises. The possibility of evil is thusly produced in a three-tier level of personal choice within the larger framework of the evolution of the universe. Moreover, the possibility of evil arises from the mind's freedom to decide.