Much of the literature builds on the thinking of American economist Frank Knight, who a century ago came up with a way to classify the things economists don’t know about.1 Knight used the word “risk” for situations where it is possible to calculate the probability of various outcomes. The term “Knightian uncertainty” came to refer to situations where calculating the odds is impossible.
In reality, most situations fall  1  F. H. Knight, Risk, Uncertainty and Profit (Boston, MA: Hart, Schaffner & Marx; Houghton Mifflin Co., 1921). -3somewhere between these two extremes, but the notion of Knightian uncertainty remains pertinent today.