Decisions in Branching Time

This chapter extends the deontic logic of Horty (Agency and deontic logic, 2001) in the direction of decision theory. Horty’s deontic operator, the dominance ought, incorporates many concepts central to decision theory: acts, causal independence, utilities and dominance reasoning. The decision theory associated with dominance reasoning, however, is relatively weak. This chapter suggests that deontic logic can usefully be viewed as proto-decision theory: it provides clear foundations and a logical framework for developing norms of decision of varying strength. Within Horty’s framework, deontic operators stronger than the dominance ought are defined for decisions under ignorance, decisions under risk, and two-person zero-sum games.