Immanuel Kant is the greatest philosopher of the modern era, the founder of classical German philosophy. Kant's range of professional interests was unusually broad. He developed a theory of the origin of the solar system, studied earthquakes, and lectured on physics and geography. However, Kant's most important works, which truly revolutionized thought, are the so-called 'critical works' devoted to the theory of knowledge. The most important of these is undoubtedly the 'Critique of Pure Reason,' a book that revolutionized philosophy, comparable to the revolution that Copernicus wrought in astronomy. The main goal of the 'Critique of Pure Reason' is to define the boundaries of human thought, but along the way, Kant raises other fundamental questions of existence, including a new doctrine of space and time and a proof of the existence of God, which is usually called 'moral' or 'anthropological.'