Abstract: In Mencius the notion of “night energy” （夜气）and that of “dawn energy” （平旦之气）constitute an important discourse on the distinction between human and animal,which is closely tied up with the Pre-Qin gentlemen’s life rhythm formed by the four sessions of a day,namely dawn,day,dusk and night.Most Neo-Confucian masters regard the saying of “night energy” as of instructive significance insofar as cultivating the original life source or an experimental understanding of the state of mind before sentimental arousal is concerned,and believe it can be “extremely helpful” to the Confucian practitioners.Sitting in the tradition of School of mind in the Ming era,Wang Yangming and Zhan Ruoshui became the guardians of “night energy”,to whom “night energy” provides an expedient method for experiencing one’s innate conscience and heavenly Principle.The theory of “night energy running through day and night” not only embodies their common pursuit for “one methodology”,but also reflects the spiritual temperaments of Ming Confucians in the School of mind—depth,quietness,concentration,and inwardness.By contrast Wang Fuzhi at the turn of the Ming and Qing dynasties was the “disenchanter” of the “night energy” discourse and the “son of the day”,whose thesis statements such as “day energy is purer than night energy” and “night energy is powerless” demonstrate a philosophical ethos of vigorousness and activity.For both the guardians of night energy and the son/children of the day,what is “guarded” or “preserved” is no other than the authentic nature of human being,a source of moral creativity that is derived from the Heaven and can be experienced and practiced in human life.