The Confucian idea of human nature is based upon the conception of the requirements of the whole man. The main purpose of this paper is to take this idea as a basis, and to compare it with the Taoist idea of human nature and the Legalist one, both of which are based only on one aspect of the requirements of man. And further this Confucian idea will be compared with the ideas of Plato, Aristotle, and Christianity. This paper also points out the relation between the Chinese traditional culture and the above-mentioned Confucian idea, and the ideas of Plato, Aristotle, and Christianity. This paper finally gives an account of the outlook of the human culture in the 21st century by virtue of the Confucian idea of human nature.