Defaults and Reasons Time and Place

This is an experimental seminar, organized around an idea, or a hope. The idea is that default logic can be used to develop a formally precise theory of reasons—what they are, how they interact— and that this theory can then be applied to other areas of philosophy in which talk of reasons is common, such as ethics or epistemology. In order to explore this idea, we will have to spend some time understanding default logic—more particularly, prioritized default logic, and more particularly still, prioritized default logics in which it is also possible to reason, by default, about the priorities among defaults. I will try to guide you through this work as gently as possible, but there is no question that some of it is complicated and technical; students enrolled in the seminar should be prepared to read papers in logic. They should also be prepared to read papers that are not in logic, but in ethics or epistemology, and in this case I hope they will be willing to explain to me what is going on. I mean that. Given the experimental nature of the seminar, I’m not exactly sure how things will develop, but I do have the first part of the course pretty well mapped out. We’ll begin by looking at (A) Raymond Reiter’s classic paper on default logic, along with bits of nonmonotonic inheritance reasoning. Then, to illustrate the applicability of default reasoning, we’ll look at (B) some of the literature on normative conflicts (“moral dilemmas”), the problems they create for deontic logic, and how defaults can help. After that, we’ll turn to (C) a careful study of prioritized default logics, as well as, possibly, (D) the alternative fomalism of argument systems, although this latter topic may be skipped entirely. At this point, we’ll move on to applications, beginning with (E) moral particularism, Jonathan Dancy’s argument from “reason holism” to particularism, and a suggestion, based on our study of default logic, about how we might allow for reason holism without being forced into particularism. We may then turn to (F) some comparisons between the account of default reasoning developed in this course and John Pollock’s theory of defeasible reasoning in epistemology. This is as far as I’ve got; after this, I’m not sure where to go. We can decide as a class what to look at next, but some options include: (G) some recent literature on the significance of disagreement among peers in epistemology and its relation to multiple extension in default logic; (H) the epistemic significance of “floating conclusions” in nonmonotonic reasoning; (I) constructivism as a metaethical position; and (J) legal rules, case law, and precedent.