Jeffrey Friedman has attempted to make a case for limiting state social engineering that is based on the skeptical epistemology of Sir Karl Popper. But Popper's epistemology is flawed, both in its rejection of a priori theorizing and its insistence on empirical falsification rather than confirmation. Classical liberalism of the sort that Friedman advocates requires, as its basis, positive knowledge of economics and social reality—not Popperian skepticism.