Abstract: Mencius's theory of goodness of human nature is not only a theoretical possibility and logical necessity,but also containing innate content of the existence.The chapters six,seven,eight of Gaozi Upper Chapters in Book of Mencius are called “three chapters about capability”in this paper.All that he says about “capability” are to present the “Conscience”or “benevolence and righteousness”based on the emotions of likes and dislikes which are similar for people.“Conscience”accepts or rejects things according to emotions of likes and dislikes,which must appear to different kinds of beginnings in different situations.Mencius raises “four primaries”to illustrates the logical connotation of the “primaries”,but the so-called “primaries”are not limited to the “four primaries”.All the “primaries”of the heart is neither a preset moral emotion which is ready-made innately,nor a composed empirical emotion.The “primaries”are the modal performance of the original form of the mind in the concrete circumstances,which unite intuitive knowledge with intuitive capacity.It shows that the mind not only agrees with the moral rules of benevolence and righteousness on the rational,but truly own the benevolence and righteousness in the inner world of emotional experience.It possesses the innate talent of goodness.Therefore,Mencius's theory of goodness of human nature is a kind of apodictic “goodness”,rather than just a possibility “goodness tendency”.

Key words: “才”(capability), three chapters about capability of Mencius, “端”(primaries), “四端”(four primaries), Conscience, goodness of human nature