The dominant strain of Confucian thought stressed the perfectibility of man. Confucius (a political philosopher who lived c. 551-479 B.C.) expressed a belief in the fundamental similarity of all persons and in the perfectibility and educability of each individual. Mencius and Hsun Tzu, two of his prominent successors, held different views on human nature, Mencius arguing that it contained the seeds of goodness, and Hsun Tzu that, in its uncultivated state, human nature tended to evil. Both, however, believed that human beings were perfectible through self-cultivation and the practice of ritual. From the 11th century onward, Neo-Confucian philosophers, engaged in the renewal and elaboration of Confucian thought, subscribed to the Mencian line, stressing the potential goodness of human nature and the importance of developing that goodness through education.