 Popper’s ideas represent the most important development in the philosophy of the twentieth century; an achievement in the tradition—and on the level—of Hume, Kant, or Whewell. … More than anyone else, he changed my life. I was nearly forty when I got into the magnetic field of his intellect. His philosophy helped me to make a final break with the Hegelian outlook which I had held for nearly twenty years. (PDI: 139.)