What can we know? What should we do? What can we hope for? Best known for his Critique of Pure Reason , German thinker Immanuel Kant based his philosophy around these fundamental questions of human experience. His most intriguing writings are excerpted here, including his The Doctrine of Virtue , Critique of Practical Reason , The Moral Law , and other seminal works, each revealing the critical analysis that keeps Kant among the most influential of modern philosophers.