Abstract: The pre-Qin Confucians believed that public interest came from the private one. And the private was the starting point of the public and was helpful to the development of the public. The relation between the two was contingent. And emotion functioned as a link. In his Republic, Plato thought that the two were in opposition. And the private was the fatal threat to the public. The growth of the public is based on the constraint of the private. And the two were separate. The realization of the public takes reason as its tool.