The thesis of yifa and weifa in The Doctrine of the Mean is very significant and complex,for it involves some most fundamental and profound problems in the Chinese philosophy.Since the Song dynasty,it is an important theme discussed among the Confucianist philosophers.Zhu Xi interprets and elucidates it creatively on the basis of the studies of Chen Hao and Chen Yi.His thought on the thesis constitutes the core of his philosophy.Through the creative interpretation of the thesis Zhu Xi proposes a series of original ideas,first of all,of Confucian orthodoxy,which constitutes the basis and starting point of his concept of mind.Zhu Xi develops the idea of respect of Chen Hao and Chen Yi into his theory of moral cultivation systematically,in order to demonstrate how human mind can be transcended and become Dao mind,and they are one mind at bottom.However,Zhu Xi still inclines to include and substitute heaven with mind after all.