Mencius saw Tian as the source of morality and social sanction (if the king was good, Heaven enabled him to rule). Hsun Tzu, on the other hand, perceived heaven as dispassionate and unresponsive at best to human predicament and existence, He therefore advocated that man should not look to Tian for assistance or attempt to placate or please tian, but rather endeavor to craft his own fate (Watson, 2003). The intellectual conflict between Mencius and Hsun Tsu reminds one of the differences between an atheist and theist, and, indeed, tian was given associations that are reminiscent of God. It was from this premise that Mencius who perceived Tian to be benevolent affirmed that human nature was intrinsically good, whilst Hsun Tzu who saw Tian as the reverse perceived human nature to be born faulty and replete with greed, strife, and Freudian attributes that if not curbed and socialized would lead to man's ruination. He particularly dwelt on the wayward tendencies to mercenary profit, jealousy and hate. The commonality lies in the fact that both Mencius and Hsun Tzu believed that social custom and regulations would protect and guide man, but from thereon they differed. Whereas Mencius believed that heart/mind (zhi) would best serve to regulate man's conduct, Hsun Tzu wrote that a curriculum of music, laws, rituals, and prescribed etiquette would be the most ideal and effective regimen, and he strongly affirmed the merits of having a mentor. A proper teacher -- and Hsun Tzu -- described this ideal teacher - would be most capable of holding one in check (the proper teacher, one could posit, is the correlation to Mencius' zhi...

This proper teacher develops rituals and customs to direct one's conduct, and rituals and customs are in fact essential since without appropriate activity, one is easily apt to lapse into the natural folly of one's nature. Just as governments need laws and regulations to guide them otherwise they would lapse into anarchy (since that is their natural state) ipso factor, humans need the same (since folly is their natural state too) (Watson, 2003).
However, similar to Mencius, Hsung Tsu believes that humans have the capacity to become good by living in the right environment and by affiliating with positive influences. Their beginning premises may be different: Mencius argues that humans are born good and that environment can augment and shape this goodness, whilst Hsun Tzu affirms that humans are born negative and that environment can save a person from ruin. However, in essence, neither are contradictory to one another since their beginning premises can end as the conclusions to the opposing other. Mencius' 'good nature' can become that of Hsun Tzu's when man is placed into the right environment, whilst Hsun Tzu's negative nature can become the conclusion of a creature devised by Mencius who ends up in a destructive environment. In this way Mencius' view that Human Nature is Good can be reconciled with Hsun Tzu's theory that Human Nature is Bad.

Source

Lau, D.C. (1970) Mencius. London: Penguin.

Shun, K.L. (1997). Mencius and early Chinese thought. CA: Stanford Univ. Press.

Watson, B. (2003). Xunzi: Basic Writings. Columbia University Press.