Abstract: Develops deontic logic against the background of a rigorous theory of agency in branching, or indeterministic, time. It is often assumed that the notion of what an agent ought to do can be identified with that of what it ought to be that the agent does. The book provides a framework in which this assumption can be formulated precisely and shown to be mistaken. In its place, it offers an alternative account of what agents ought to do that relies on an analogy between action in indeterministic time and choice under uncertainty, as it is studied in decision theory. This alternative account is then related to issues involving conditional obligation, group obligation, act utilitarianism, and rule utilitarianism.

Keywords: act utilitarianism, action, agency, branching time, conditional obligation, decision theory, deontic logic, group obligation, indeterminism, rule utilitarianism