Sir Karl Popper was one of the most prolific philosophers of the 20th century, and remains one of the most influential. His most significant academic contributions were in the philosophy of science, and he collaborated with several scientists. His social and political philosophy was largely responsible for his extra-academic fame, and has had more impact. Overall, his work was exceptionally broad. He also made contributions to ancient philosophy, epistemology, metaphysics, philosophy of biology, philosophy of education, philosophy of history, philosophy of mind (and psychology), philosophy of physics, and the foundations of probability theory (both mathematical and philosophical).