29 March 2010, 18.30 – 20.00

Distinguished Lecture Series: José L. Bermúdez (St. Louis)

“Decision theory: Psychology and norms”

Decision theory is a mathematical theory that is called upon to play a variety of explanatory roles when used as a theory of rationality. These roles correspond to different dimensions of the concept of rationality. This paper begins by distinguishing three different dimensions of rationality – the action-guiding dimension; the normative assessment dimension; and the explanatory-predictive dimension. In my book Decision Theory and Rationality I argue that decision theory cannot serve all of these different functions simultaneously, but that they are all interdependent. This paper works through this tension in the context of how we think about the outcomes of actions.

Standard presentations of decision theory adopt some version of the invariance principle (that it is irrational to assign different utilities to propositions known to be equivalent). This normative principle raises problems for the idea that decision theory can serve as a theory of motivation, in the light of extensive experimental evidence that reasoners regularly breach the invariance principle. One way of responding, proposed by the philosopher Frederic Schick, is an intensional version of decision theory that allows a single outcome to be understood in different ways (and utilities to be assigned accordingly). This raises problems (such as the failure of the expected utility theorem) that can be dealt with by a more fine-grained way of individuating outcomes (as in Broome’s theory of individuation by justifiers). As I bring out, though, none of these strategies serves all three of the explanatory projects under consideration. The paper ends by explaining how the three explanatory projects are inexplicably linked with each other. The conclusion is that decision theory cannot be used as the core of a theory of rationality.

Professor José L. Bermúdez, Washington University St Louis, http://artsci.wustl.edu/~jlbermud/

All are welcome.



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Annette Winkelmann
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