 By locating our good nature in Pattern, however, Cheng Yi introduced new philosophical challenges. His view assumes that all human beings have Pattern at all times, and yet it is obvious that few if any human beings are good at all times, so there must be some way of explaining the pervasiveness of human moral failure. Furthermore, Pattern is shared by all beings, human or otherwise, so the nature that we identify with Pattern cannot by itself suffice to distinguish us from non-human things. Cheng’s response in brief was to posit a second sort of nature consisting of one’s endowment of qi, sometimes called the “material nature” or “the nature of one’s qi-constitution” (qizhi zhi xing 氣質之性). The nature that he identified with Pattern he called by various names, including “inherent nature” or “original nature” (benxing 本性), referring to our nature as it is when not distorted or altered by external stimuli, prior to the arousal of occurrent emotions. Both moral failure and differences in species or kind can be traced to differences in one’s qi-constitution. If human beings sometimes fail to be good and virtuous it is because of dark or turbid qi which prevents Pattern from expressing itself or responding correctly, and dark and turbid qi is ubiquitous. The configuration and quality of qi which constitutes a thing also determines the particular type or species it is (Tiwald &amp; Van Norden 2014: 166). This was a view that Zhu Xi came to both refine and popularize in his own writings and teachings (Ivanhoe 2000: 45–49; Tiwald &amp; Van Norden 2014: 170–178). But Zhu was reluctant to say that we literally have two separate natures, recommending instead that we have only one nature that can be described in different terms, as “inherent nature” when considered in terms of its intrinsic structure and as “material nature” when considering in terms of its interactions with qi (Angle &amp; Tiwald 2017: 64–67).