This text reviews a recent approach to modeling "radically uncertain" behavior in strategic interactions. By rigorously rooting the approach in decision theory, we provide a foundation for applications of Knightian uncertainty in mechanism design, principal agent and moral hazard models. We...

Duesenberry introduced the notion of a ratchet investor who does not tolerate any decline in her consumption rate. We connect the demand behavior of such an agent to the behavior of standard time-additive agents. A ratchet investor demands the running maximum of the optimal plan a conventional...

We develop a theory of optimal stopping problems under ambiguity in continuous time. Using results from (backward) stochastic calculus, we characterize the value function as the smallest (nonlinear) supermartingale dominating the payoff process. For Markovian models, we derive an adjusted...