This article presents a sketch and a comparison of two perspectives of justice. I discuss Plato’s idea of justice in the Republic (section 2), and Mencius’ thinking on the same topic in Mencius (section 3). For Plato, justice leads to harmony and reason is the key element, especially for getting hold of the good, and for unifying the different parts of the soul successfully; likewise, the philosopher should rule the polis for the unification of the three classes of people in the polis. Mencius treats yi, the concept which is comparable to justice, similarly to Plato, namely as one’s proper relationship with others, except one’s parents who are not considered as others. For Mencius, Yi is shown in one’s lifelong commitment to act appropriately in all the situations one encounters in the world. Ren is shown in one’s love of others and guides one in a more important way than reason for one’s cultivation of yi.