Richard Bradley (LSE): “Chance as the Guide to Life”

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Abstract: When choosing between two courses of action having the same two possible outcomes, we should choose the act for which the conditional chance of the preferred outcome, given its performance, is higher. This simple principle is, I argue, both a basic condition of instrumental rationality and the core of our conception of chance. To support this latter claim, I show that it in the presence of very weak rationality conditions on choice, the principle implies:

1. A version of Lewis’ Principal Principle (and that the converse is false).
2. Stochastic Dominance: a principle endorsed by all main theories of rational decision making under risk.
3. That the evidential and causal decision values of an act, conditional on the chances, are the same.

Finally, I argue that its appeal as a principle of instrumental rationality derives from the fact that higher chances of a good outcome are better than lower ones together with the fact that conditional chance of an outcome O, given some act A, measure the efficacy of A in bringing it about that O.

Richard Bradley is a Professor in the Department of Philosophy, Logic and Scientific Method, he works broadly in decision theory and related fields such as formal epistemology and semantics.