Critique of Pure Reason

What it is

This is Immanuel Kant's major philosophical book, first published in 1781 and revised in 1787. In it Kant tries to work out what reason can and cannot know, and introduces his theory of transcendental idealism, which argues that the mind actively shapes how we experience space, time and objects.

Why it matters

The book responded to earlier thinkers like Locke, Hume, Descartes and Leibniz, and tried to settle disputes between empiricists and rationalists about where knowledge comes from. Though largely ignored at first, it became hugely influential and helped launch German idealism, making Kant one of the most important philosophers in Western history.

Look closer

• Why might a book written in dense, difficult language still become so influential?
• What does it tell us about the intellectual debates of Kant's time that he felt he needed to 'critique' reason itself?
• What is missing from a title page that you might want to know about how the book was actually read or received?