Once, deontic logicians toiled over artificially simple formal systems whose predictions moral philosophers could, in general, safely ignore. But no more. A focus of contemporary deontic logic is the formal representation of the nuance and complexity of everyday normative reasoning. Horty's work is at the leading edge of these efforts. In Reasons as Defaults, he offers a rigorous formal treatment of the role of reasons in normative reasoning—both practical (reasons for action) and theoretical (epistemic reasons for belief). It is now a commonplace of moral philosophy that what an agent ought to do is determined by how the normative “weights” or “forces” of different reasons combine. But as Horty complains, these are just metaphors, and we have no systematic account of how reasons combine to determine what agents ought to do. The primary aim of his book is to correct this.
Horty seeks to both represent and explain the...
