The fourth volume of the anniversary edition contains four books by Kant, published after the Critique of Pure Reason. These are the “Prolegomena,” which are a summary of the main ideas of Kant’s main work; “Fundamentals of the Metaphysics of Morals” is the first major work on ethics; “Metaphysical Principles of Natural Science,” a work showing Kant’s keen interest in the theoretical problems of natural science; "Critique of Practical Reason", developing Kant's ideas in the ethical sphere. The translations have been re-checked with the original, the notes to the work on the philosophy of natural science have been written anew.