We investigate what it means for one act to be more ambiguous than another. The question is evidently analogous to asking what makes one prospect riskier than another, but beliefs are neither objective nor representable by a unique probability. Our starting point is an abstract class of preferences constructed to be (strictly) partially ordered by a more ambiguity averse relation. We de…ne two ...

The thesis that mental content is normative is ambiguous and has many forms. This article deals only with the thesis that normativity is connected to our mental attitudes rather than with the content of the attitudes, and more specifically with the view that it is connected to belief. A number of writers have proposed various versions of a ‘norm of truth’ attached to belief. I examine various v...

It has often been claimed that measures designed to stimulate capital formation at the national level will accelerate the decline of regions that are not growing. A number of simple models are employed to evaluate this claim, and it is found that the effect of national subsidies is ambiguous. Further, it is shown that on average the form of capital stimulus used in the Economic Recovery Tax Act...

Proximate and ultimate causes in evolutionary biology have come to conflate two distinctions. The first is a distinction between immediate and historical causes. The second is between explanations of mechanism and adaptive function. Mayr emphasized the first distinction but many evolutionary biologists use proximate and ultimate causes to refer to the second. I recommend that ‘ultimate cause’ b...

This paper develops a real options model to investigate the relationship between exchange rate movements and the occurrence of price dumping. Our results reveal that the effect of exchange rate volatility on the probability of dumping occurrence is ambiguous, depending on the level of exchange rate. The appreciation of the importing country’s currency tends to have a positive impact on the prob...

We prove that a k-dimensional hereditarily indecomposable metrisable continuum is not a Pk-valued absolute retract. We deduce from this that none of the classical characterizations of ANR (metric) extends to the class of stratifiable spaces.

This paper investigates the impact of informational ambiguity and attitude to it on security prices. Attention is focused on equilibria in which a market maker has an ambiguity in his probability assessment. We show that the equilibrium ambiguous bid-ask spread can be decomposed into the probabilistic spread and an “ambiguity premium/discount” component characterizing the ambiguity aversion/see...

Standard economic models cannot capture the fact that information is often ambiguous, and is interpreted in multiple ways. Using a framework that distinguishes between the language in which statements are made and the interpretation of statements, we show that ambiguity can have important consequences. We show that players can agree to disagree in the presence of ambiguity, even if there is a c...

We analyze the policy implications of aversion to Knightian uncertainty (or ambiguity) about the possibility of tipping points. We demonstrate two channels through which uncertainty aversion affects optimal policy in the general setting. The first channel relates to the policy’s effect on the probability of tipping, and the second channel to its differential impact in the preand post-tipping re...