In Chapter 4, I address humanism as a moral foundation for capitalism by discussing the lives and writings of Karl Polanyi and John Maynard Keynes. The narrowing of political economy by nineteenth-century classical economists was challenged on two fronts. Some economists fought to maintain a broad social and moral perspective, but some economists turned the narrowing theory of classical economists into a stinging rebuke of capitalism itself. I begin by discussing the rising influence of humanism in the twentieth century. Next, I discuss the Hungarian-Austrian political economist Karl Polanyi and his critique of capitalism based on humanism. Although he was initially attracted to Marx’s moral critique, Polanyi eventually rejected Marxism on similar grounds as Tawney. In his search for a moral foundation for capitalism, Polanyi rediscovered the moral theory behind Adam Smith’s writings. I then discuss the British political economist John Maynard Keynes. Similar to Polanyi, Keynes rejected the narrow utilitarianism of both Marx and the classical economists in forming his moral foundation for capitalism based on responsibility and duty. This sets up a discussion of humanism as a moral foundation for capitalism based on Polanyi’s and Keynes’s seminal works.