Abstract
We distinguish three qualitatively different types of uncertainty—ethical, option and state space uncertainty—that are distinct from state uncertainty, the empirical uncertainty that is typically measured by a probability function on states of the world. Ethical uncertainty arises if the agent cannot assign precise utilities to consequences. Option uncertainty arises when the agent does not know what precise consequence an act has at every state. Finally, state space uncertainty exists when the agent is unsure how to construct an exhaustive state space. These types of uncertainty are characterised along three dimensions—nature, object and severity—and the relationship between them is examined. We conclude that these different forms of uncertainty cannot be reduced to empirical uncertainty about the state of the world without inducing an increase in its severity.
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Notes
The program is available online at http://www.bbc.co.uk/programmes/b01hxmx1.
This is not of course to say that it is the only view being expressed. Inevitably such a broad characterisation of the state of thinking in a field will be a bit of a caricature and it is quite possible that nobody holds the default view in its completely unqualified form.
See Popper (1959) for an early statement of this argument.
Though, as Binmore (2009) emphasises, Savage only held that this applied in small-world decision making.
This epistemic reading of ambiguity aversion is not the only one to be found in the literature. See, for instance, Fox and Tversky (1995).
An argument of this kind has been made for the case of Knightian uncertainty by Bewley (1986).
The term ‘ethical’ is used here in the same way that it is used by Ramsey, to denote that which has to do with what matters to the agent. It is not meant to be read as having only to do with morality.
This is broadly the same conclusion as is reached by Broome (1991).
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Acknowledgements
We would like to acknowledge the support of the Arts and Humanities Research Council (Grant Reference: AH/I003118/1), The Netherlands Organisation for Scientific Research (Grant Number 236-20-005), and the Fonds National de la Recherche Luxembourg (Grant Number 09-194). We are grateful to Hykel Hosni and Casey Helgeson for their comments on an earlier draft.
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Bradley, R., Drechsler, M. Types of Uncertainty. Erkenn 79, 1225–1248 (2014). https://doi.org/10.1007/s10670-013-9518-4
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DOI: https://doi.org/10.1007/s10670-013-9518-4