"Criticism of practical reason" - the main ethical treatise of Immanuel Kant, developing the ideas of his "Criticism of pure reason" and exploring in detail the concept of the categorical imperative - the highest principle of morality. According to the philosopher, a person can be truly happy only if he realizes that he is worthy of happiness. And this can be achieved only by performing a duty, that is, by following the moral law .. According to Kant, doing so a person, regardless of external circumstances, sensory needs and other motives, becomes truly free. One of Kant's leading translators into Russian was the poet, literary critic and critic Nikolai Matveevich Sokolov (1860-1908). Having translated the main treatises of Kant, he later presented his other works to Russian readers. Sokolov's translations are considered accurate and complete, they were repeatedly reprinted in Soviet times. Like other books in the Great Ideas series, the book will be simply indispensable in the library of students of humanities, as well as for those who want to get acquainted with key works and ideas of world philosophy and culture.