Abstract: In Kant's educational thought, he observes two steps in one's reaching adulthood, that is, through being wayward and disorderly to disciplined, and then from which establishing moral laws. One lives waywardly, which is a disorderly state. It is therefore necessary to discipline him through education by imposing a code of conduct on him. Education limits his freedom to create the habit of living in people's lives so as to let one to perform one's freedom in a certain behavior pattern. In this point of view, education is the starting point of enlightenment. When analyzing educational activities, Kant feels the paradox of education (the external power) and enlightenment (the internal power), and he conceives this paradox as the major dynamical power in one's reaching adulthood. Yet, when one has obtained adulthood, one will be able to improve oneself in freedom alone and no longer need external intervention by education which is regarded as a free register. However, through an in-depth analysis, one will then be unable to accomplish morality in practice only by the freedom of people, without the paradox of education and enlightenment. In this observation, Kant's religious thought is incomplete in practice.