“Critique of Pure Reason” is Kant’s fundamental work, which became the starting point in the history of world philosophical and scientific thought.
It’s an excellent, serious school of logical thinking, although studying and understanding Kant isn’t easy. After Kant, the subtle thought that had ripened through critique became extremely distrustful and cautious—not only toward solutions, but also toward the very posing of questions about human knowledge—which, in turn, opens the path to genuine scientific inquiry in attempts to bring together the conclusions of individual sciences.