Knightian Decision Theory: Part 1
A theory of choice under uncertainty is proposed which removes the completeness assumption from the Anscombe-Aumann formulation of Savage’s theory and introduces an inertia assumption. The inertia assumption is that there is such a thing as the status quo and an alternative is accepted only if it is preferred to the status quo. This theory is one way of giving rigorous expression to Frank Knight’s distinction between risk and uncertainty.
Bewley, Truman F., "Knightian Decision Theory: Part 1" (1986). Cowles Foundation Discussion Papers. 1050.