The doctrine for which Mencius is best known, and his most influential contribution to Chinese thought, is the claim that human nature is innately good (xing shan). Against those who held that nature is neutral or self-interested, Mencius argued that every person is born with the "four sprouts" or beginnings of virtue: the feeling of compassion, which is the sprout of humaneness (ren); the feeling of shame, the sprout of righteousness (yi); the feeling of deference, the sprout of ritual propriety (li); and the sense of right and wrong, the sprout of wisdom. His famous illustration is that anyone who suddenly saw a child about to fall into a well would feel a spontaneous alarm and pity: proof, he held, that moral feeling is native to the heart, not imposed from without.
Moral cultivation is therefore not the manufacture of virtue but the nurturing of these innate sprouts until they grow to maturity, as a farmer tends young plants. Mencius also taught that the ruler holds the Mandate of Heaven only so long as he cares for the people's welfare, and that a tyrant who loses their hearts may justly be removed.