The Doctrine of the Mean is one of the major Confucian classics focusing on natural justice and its political implications via cosmic dynamics and its harmonious eternity. The rule of the saints modeling themselves after the heaven’s virtue is advocated as the so-called rule of man, or the rule of virtue, in which natural harmony in the cosmos is believed to be the manifestation of eternal and universal justice. Both the editors of The Doctrine of the Mean in pre-Qin dynasty and its commentators in the Tang dynasty have availed themselves in repudiating the legalist utilitarianism abused in the despotic Qin dynasty and empty-world thoughts of Buddhism prevalent in the Tang dynasty by virtue of natural justice and cosmic fairness in heaven-mandated- nature theory. Their academic endeavors are directed at consolidating cosmological faith and moral fairness for Confucian political ideology in self-disciplining, family establishing, country ruling, and world harmonizing.