This paper examines the idea of xing 性 in Guo Xiang's Commentary on the Zhuangzi in order to show the distinctiveness of Guo's thought. I argue that, for Guo, xing is individualized and subject to no external standard, not even to the "normal" condition proposed by the primitivists in the Zhuangzi. Regarding the debate about xing's changeability, I argue that one's xing can change over time, even by learning, although this change is constrained within certain boundaries. The individualization of xing and the need of holding to one's boundaries serve to explain the emergence of social norms, which can and should be established in a way that respects different xing. This dynamic between individuality and social organization contributes to our thinking about fundamental tensions in human life.