 The differences between Mencius’ and Xunzi’s theories are substantial and raise sophisticated philosophical issues that remain relevant to this day. Xunzi launched a vigorous critique of Mencius’ claim for the existence of natural tendencies that form the basis for development of a good person. In arguing against Mencius, he presupposes a strict separation between that which is given in human nature and that which must be developed through deliberate effort. Mencius’ conception of human nature, on the other hand, presupposes that what is in human nature can be something that can be further developed along tendencies that are given but need to be triggered by interaction through learning in the right environment. Their differing conceptions of human nature exemplify a variability and ambiguity in conceptions of human nature that is a subject of analysis for contemporary philosophers of science (see Griffiths, 2002; Wong, 2015a). Furthermore, Mencius and Xunzi differ in their theories as to whether ethical norms and values are discovered or invented, with Mencius’ theory construing them as part of the order established by Heaven, and Xunzi’s theory construing them as constructed by human beings to solve problems for cooperation arising from the self-seeking and competitiveness of human nature.