Philosopher who posed the question "What can I know?"

KANT

This German thinker from Königsberg wrote Critique of Pure Reason and argued that knowledge is shaped by the mind’s own structures.

This clue refers to Immanuel Kant, the 18th-century German philosopher famous for exploring the limits of human knowledge. His work Critique of Pure Reason directly tackles the question "What can I know?"—a core theme in his philosophy. The answer is simply his last name, "KANT," with no wordplay or hidden tricks involved. If you’ve heard of his ideas on ethics or metaphysics, that’s a good hint.