The philosopher Immanuel Kant is often referred to by his last name, Kant, which is a four-letter word. He was a German philosopher who lived in the 18th century and is widely regarded as one of the most influential thinkers of modern Europe. He is best known for his work in the fields of metaphysics, epistemology, ethics, and aesthetics. His most famous works include Critique of Pure Reason, Groundwork of the Metaphysics of Morals, and Prolegomena to Any Future Metaphysics.