|The aim of this article is to consider the problematics of cosmology and ethics shown in Cheonmyungdoseol (Explanation of the Diagram of the Heavenly Mandate) by comparing with "Taijitushuo" (Explanation of the Diagram of the Supreme Ultimate). Cheonmyungdoseol is originally the work heading for the objective scientific cosmology like "Taijitushuo". However, though Cheonmyungdoseol shares the cosmological frame of "Taijitushuo" like the li-qi theory, objectivism, and anthropic principle, the perspective in the basis is distinct from "Taijitushuo". That is to say, "Taijitushuo" stands for the eternalism in cosmology, while Cheonmyungdoseol possesses the presentism that regards the past and the future are composed according to the present point of view. In particular, Cheonmyungdoseol reflects the idea that one should realize tianming (the Heavenly Mandate, cheonmyung in Korean) endowed to an individual in his own consciousness and cognitive function. The difference of perspective is brought about by the concept of tianming whose implication and boundary are different from taiji (the Supreme Ultimate). The taiji refers to a cosmological principle as ultimate reality from the objective point of view, while tianming indicates one``s job and moral principles which one has to see in his mind. Therefore, tianming is related with the consciousness of "ought", because it would not be able to be realized without self-cultivation. In this regard, Cheonmyungdoseol cannot but adopt the subjectivism in the end. These two perspectives in cosmology are closely interrelated to the different ethical viewpoints that appear in the Four-Seven Debates between Yi Hwang and Ki Dae-seung. While Ki Dae-seung adheres to the objectivism which sees that the criterion to determine moral good and evil lies on whether one``s cognition can accord with the social norms, Yi Hwang gradually declines to the subjectivism which regards the consciousness of "ought" as the ultimate criterion of morality. In other words, Ki Dae-seung``s ethical perspective is to supplement the presentism and phenomenalism of Cheonmyungdoseol with objectivism, while Yi Hwang``s position represents the completion of subjective ethics based on Cheonmyungdoseol. According to Yi Hwang, the consciousness of "ought" can be regarded as the manifestation of tianming as the awareness of one``s job and moral principles. After all, parting from the cosmology where Cheonmyungdoseol originated, Yi Hwang``s theory of mutual manifestation ironically stands in line with the moral theory centering on the subjective mind and cognition.