This paper has three aims: first, the main objective is to put the rediscovery of genuine Knightian uncertainty after the (2008) financial crisis in conceptual and historical perspective; I do so by way of an extended analysis of the changes in twentieth century economics. The second, more tentative aim is to offer a characterization of the significance of uncertainty and technocracy in twentieth century mathematical economics and Rawls’s (early) political philosophy. I will argue that despite the strong criticisms of Rawls by Arrow (and Harsanyi), the three share a commitment to what I will call the ‘technocratic conception of politics,’ which finds it very difficult to accept genuine uncertainty. But upon close inspection it turns out that Rawls and Arrow disagree on how to handle uncertainty.  The core of the paper is a historical investigation of the conceptual shifts during during the formal revolution in mathematics. In it, I argue, third, that true uncertainty got displaced by successor concepts in mathematical economics that are neither identical to it nor to each other.