Normative, Subjunctive and Autoepistemic Defaults.
Craig E. Boutilier · 1992
We explore the relationship between theories of nonmonotonic inference and belief revision using modal and conditional representations. We demonstrate that the logics governing belief revision and conditional default reasoning are identical by showing that the normative and subjunctive conditionals, defined in a modal logic CO* in earlier work, have precisely the same formal truth conditions. This can only be achieved by a strict adherence to the Ramsey test in our formulations. Hence, we must take pains to avoid the celebrated triviality results. We explain this formal similarity, the practical considerations that distinguish the two types of reasoning, and how default reasoning can be viewed as a special case of belief revision. We then show that autoepistemic logic can be generalized within this framework and discuss the relationship between autoepistemic, normative and subjunctive defaults.