A critique of rationalism, this book aims to explain both its powerful contributions to mathematics and the physical sciences, where our arithmetical, geometrical, and mechanical intuitions have had a highly productive role in the development of pure theory, and its disastrous failures in cosmology and the moral sciences. In these supposed sciences, rationalism has all but destroyed the social conscience of the West by creating the disastrous political philosophy of neoliberalism. To reset our moral compasses, we must develop new, socially just versions of the old welfare states. And to restore democracy we must return to Keynesian economic management.