In this paper, I focus on the four concepts of "Xin心/Mind-heart ", "Yi意/Will", "Zhi知/Knowing", and "Wu物/Thing" to elucidate Wang Yang-ming's philosophical system. With regard to this purpose, it is necessary to introduce and explain firstly the concept of "Li理/Principle", and then I discuss the fundamental doctrine of "the identity of Mind-heart and Principle心即理" whose validity, in my view, is reduced to the moral domain. Secondly, I give a detail account of the rest concepts of "Yi", "Zhi", and "Wu", respectively derived from "Cheng-Yi誠意/Sincerity of the will", "Zhi-Zhi致知/Extension of knowledge", and "Ge-Wu格物/Investigation of things" in The Great Leaning〈大學〉, to illuminate the theory of moral cultivation in Wang Yang-ming's philosophy. At last, through the analysis of the discussion of“Four Maxims”四句教between Wang Yang-ming and two of his pupils, Qian Xu-shan and Wang Long-xi, my interpretation of the four concepts foregoing is confirmed and the point that the connection between Ben-Ti本體/original substance and Gong-Fu工夫/moral cultivation is emphasized.
Keywords：Wang Yang-ming, Xin, Yi, Zhi, Wu, Four Maxims