"Critique of Practical Reason" is a fundamental philosophical treatise by the German thinker Immanuel Kant. In this work, the author examines the issues of morality, ethics and free will, and also examines the concept of categorical imperative. Kant analyzes the nature of duty and morality, explaining what inner freedom and responsibility are. In his work, he argues for the idea of a moral law that is universal and necessary for all rational beings. "Critique of Practical Reason" is an important work for understanding ethical principles and fundamental moral values.