Knightian uncertainty

Knightian uncertainty refers to a type of uncertainty that cannot be quantified or measured, unlike risks which can be expressed in probabilities. The term originates from the work of economist Frank H. Knight, particularly in his 1921 book "Risk, Uncertainty, and Profit." In this context, Knight differentiated between risk (where the probabilities of different outcomes are known) and uncertainty (where those probabilities are unknown or cannot be reliably estimated).