In familiar models, a decrease in the friction facing mobile factors (e.g., lowering their adjustment costs) increases a coordination problem, leading to more circumstances where there are multiple equilibria. We show that a decrease in friction can decrease coordination problems if, for example, a production externality arises from a changing stock of knowledge. In general, the relation betwee...

Well Founded Semantics is adequate to capture nonmonotonic reasoning if we interpret the Well Founded model of a program P as a (possibly incomplete) view of the world. Thus the Well Founded model may be accepted to be a definite view of the world and the extended stable models as alternative enlarged consistent belief models an agent may have about the world. Our purpose is to exhibit a modula...

A weak concept of compactness for nonmonotonic logics is proposed, which is suitable for several nonmonotonic logics, for which Makinsons smallest cumulative extension as well as Freund/Lehmanns canonical extension fail.

This paper explores the role of some basic notions in the study of non-monotonic reasoning, such as validity, logical consequence, context, rules and assumptions. It offers some considerations about the relation between non-monotonicity and the ideal of perfect validity in logical inference and the pertinence of taking into account human limitations. I propose that work on non-monotonic reasoni...

Ford has introduced a non-monotonic logic, System LS, inspired by an empirical study of human non-monotonic reasoning. We define here a defeasible logic FDL based on Ford’s logic, and in doing so identify some similarities and differences between Ford’s logic and existing defeasible logics. Several technical results about FDL are established, including its inference strength in relation to othe...

In this paper we investigate nonmonotonic ‘modes of inference’. Our approach uses modal (conditional) logic to establish a uniform framework in which to study nonmonotonic consequence. We consider a particular mode of inference which employs a majority-based account of default reasoning—one which differs from the more familiar preferential accounts—and show how modal logic supplies a framework ...

In this paper, we provide a nonmonotonic logic for analogical reasoning and a graphical representation method to facilitate the calculation of analogies.

This paper develops two conditional logics that allows one to reason about the belief of another agent (which reasons in conditional logic himself). The desirable properties of such logics that reason about the beliefs of another non-monotonic agent are discussed and the two logics proposed here are shown to have those properties.

I’ll describe a range of systems for nonmonotonic conditionals that behave like conditional probabilities above a threshold. The rules that govern each system are probabilistically sound in that each rule holds when the conditionals are interpreted as conditional probabilities above a threshold level specific to that system. The well-known preferential and rational consequence relations turn ou...