Abstract

From Groundwork for the metaphysics of morals and Critique of practical reason, we can deduce Kant's interpretation of the concept of freedom, which has undergone a change from practical freedom to transcendental freedom, and the deduction of freedom has been perfected, the rational facts have been put forward to provide the basis of free deduction. The reason for the change is that freedom as the basis of theoretical practice is assumed and predetermined, how the cause and effect of freedom as will may not be explained, and the nature of freedom is not defined clearly, the legitimacy and authority of the moral law is not established. After the transformation, the problem was solved. Although rigour raises questions about the universality of Kant’s moral law, Onora Sylvia O’Neill and others argue that Kant’s moral law is a product of virtue ethics, not a normative ethic, Kant's moral law still can instruct us in ethical life.