 In the fourth quadrant, knowledge is uncertain and consequences are large, requiring more robustness.According to Taleb, thinkers who came before him who dealt with the notion of the improbable, such as Hume, Mill, and Popper focused on the problem of induction in logic, specifically, that of drawing general conclusions from specific observations.The central and unique attribute of Taleb's black swan event is that it is high-profile.