Immanuel Kant (1724-1804) was an Enlightenment thinker who lived in the 18th century. At a time when people discarded morality, he declared the importance of duty as an objective and universal concept. For Kant duty is a binding moral principle because it is a categorical imperative. Kant’s aesthetic writing can be seen as an extension of his moral theory, to go beyond subjective views towards almost entirely objective judgements. In politics, he focused on the subjectivity reason based on the will of nature, which enlightens mankind and promotes its felicity. By illustrating the distinction and correlation between subjectivity and objectivity in Kant’s philosophy, this paper is connecting several aspects of Kant’s thought in order to demonstrate the importance of his theory to mankind.