Mainstream economics is one way of understanding how the economy works, but mainstream economists argue much more: that mainstream economics is the only way of understanding the economy. Mainstream economists should embrace pluralism for reasons suggested by John Stuart Mill: as a guard against the tyranny of the majority, a tyranny that fortifies itself against doubt not by reason but by power; even if the majority is right and the doubters wrong, engaging with doubt is a way to strengthen correct arguments; and, most likely, according to Mill, there is partial truth on the side of heterodoxy as well as on the orthodox side. The two elements of the power of mainstream economists are related: the police power over what is and what is not published in the major journals, and the role of publication in these journals in the tenure process. Pluralism is not an issue of concern to academics only. Economists of all stripes may try to construct the economy in the image of their theories, but for some time the mainstream has had the upper hand, just as it does in the academy. The push to deregulate the economy, which began in the United States during the Carter presidency, had its full flowering in the financial crisis of 2008. What will it take to allow heterodoxy into the academy? If history is any guide, innovations in economics take root when they are allied to successful political movements. One case in point is the symbiosis between Keynes’s General Theory and the New Deal and social democracy. Another is the resurgence of pre-Keynesian theory dressed up in the high-tech mathematics of New Classical theory and the coming to power of the apostles of neoliberalism in the 1980s. It’s a good bet that for a new economics to take hold in this century, it will do so in partnership, however tacit, with a new politics.