In the discussion of doing good, Xun Zi approached the phenomenon of ”being capable but unable to do something.” According to Xun Zi's doctrine, if one didn't do something that he or she was capable of doing, it was due to the fact that he or she was not willing to do it. Therefore, such a phenomenon was related to the will or willingness in a moral act. On this issue, Xun Zi was somewhat similar to Aristotle, but what differentiated him from Aristotle was: the will or willingness as Xun Zi understood it was not totally an individual's active and free choice but something more or less inevitable. Also, according to Xun Zi, one's wish to do good was indeed the result of the evilness of human nature, since Xun believed that one would automatically seek to make up for the things in shortage. This theory of shortage reminds us of Augustine's explanation of evil. Though both of them mentioned the freedom of will, Xun and Augustine were trying to resolve different problems. Moreover, they were drastically distinct in their understandings about shortage and in the conclusions they respectively made.