Bradley, Seamus
(2012)
Scientific uncertainty and decision making.
PhD thesis, London School of Economics and Political Science.
Abstract
It is important to have an adequate model of uncertainty, since decisions must be
made before the uncertainty can be resolved. For instance, flood defenses must be
designed before we know the future distribution of flood events. It is standardly
assumed that probability theory offers the best model of uncertain information. I
think there are reasons to be sceptical of this claim.
I criticise some arguments for the claim that probability theory is the only
adequate model of uncertainty. In particular I critique Dutch book arguments,
representation theorems, and accuracy based arguments.
Then I put forward my preferred model: imprecise probabilities. These are sets
of probability measures. I offer several motivations for this model of uncertain
belief, and suggest a number of interpretations of the framework. I also defend
the model against some criticisms, including the so-called problem of dilation.
I apply this framework to decision problems in the abstract. I discuss some
decision rules from the literature including Levi’s E-admissibility and the more
permissive rule favoured by Walley, among others. I then point towards some
applications to climate decisions. My conclusions are largely negative: decision
making under such severe uncertainty is inevitably difficult.
I finish with a case study of scientific uncertainty. Climate modellers attempt
to offer probabilistic forecasts of future climate change. There is reason to be
sceptical that the model probabilities offered really do reflect the chances of future
climate change, at least at regional scales and long lead times. Indeed, scientific
uncertainty is multi-dimensional, and difficult to quantify. I argue that probability
theory is not an adequate representation of the kinds of severe uncertainty that
arise in some areas in science. I claim that this requires that we look for a better
framework for modelling uncertainty
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