Immanuel Kant's Critique of Practical Reason is a fundamental philosophical treatise exploring the concepts of morality and the moral law. In this work, the author examines the issues of free will, justice, moral imperative and responsibility. Kant argues that actions should be based on the imperative of categorical morality, which recognizes each person as a subject of moral autonomy. This work became one of the most important works of the German Enlightenment and influenced the further development of ethics and philosophy. "Critique of Practical Reason" remains a relevant and important work for understanding moral issues and principles in the modern world.