性善論是孟子哲學的思想核心，強調道德根本源自於人性，他依此區分人與禽獸之間的差異，並以內在的「四端之心」說明「性善」的價值根源與道德主體的表現；荀子提出性惡論，言若人順性而為，必將歸於惡，所以必須「化性起僞」，主張用外在「君師」、「禮法」的力量，感化並改造人原本的惡性。 德國哲學家康德提出「二律背反」之辯證法，意指對同一個對象或問題所形成的兩種理論或學說，雖然各自成立但卻相互矛盾的現象。他點出人們在現實生活中「德行與幸福的矛盾」：「德行」是靈魂想要追求至善的完美境界，而「幸福」是人自然情欲的感性本質，即是所謂「實踐理性的二律背反」，而孟子性善與荀子性惡與其論點頗具相似之處，便是本文所討論的宗旨。

Good human nature is the core value of Mencious’ philosophy, and he emphasized that morals originated from human nature, which set humans apart from animals. He also used the “four cardinal virtues” to illustrate the root and expression of good human nature. On the other hand, Xunzi suggested evil human nature where humans must do evil if they follow their instincts; therefore, he advocated the need of education, “kings and teachers” and “etiquette and law” to influence and transform the instinctive evil. In addition, German philosopher Kant proposed the dialectical method as “antinomies”, meaning the two theories or explanations that elucidate one subject or problem are both contradicting yet convincing at the same time. Kant pointed out that humans live in a world of conflict between virtue and happiness. Virtue is a perfect state of ultimate goodness where a soul wishes to achieve, while happiness is the outcome of humans original lust, and the two concepts are the “antinomies” of rational practice. Kant’s concept can be compared to the theories of human nature by Mencius and Xunzi, and therefore is the main focus of this study.