This paper argues that yu 欲 (desire), in Xunzi’s view, cannot by itself motivate action. Such a clarification will also bear on our understanding of the relation between xin 心 (the heart/mind) and yu in the Xunzi. This paper is divided into three main sections. The first section seeks to explicate the common assumption that yu can be an independent source of motivation. In the second section, I will conduct textual analysis that challenges such an assumption and argues that only (...) xin can by itself motivate action. In the third section, I explain that the issue of whether yu can conflict with xin is not applicable in Xunzi’s thought and extrapolate the implications that xin is always activated and that xin has natural inclination to pursue the objects of yu. For these reasons, the source of moral failure lies in xin being active in certain problematic ways. (shrink)