There was a long tradition in philosophy according to which good reasoning had to be deductively valid. However, that tradition began to be questioned in the 1960’s, and is now thoroughly discredited. What caused its downfall was the recognition that many familiar kinds of reasoning are not deductively valid, but clearly confer justification on their conclusions. Here are some simple examples.

An extended review of what is known about the formal behaviour of nonmonotonic inference operations, including those generated by the principal systems in the artificial intelligence literature. Directed towards computer scientists and others with some background in logic.

inheritance reasoning in semantic networks allowing for multiple inheritance with exceptions. The approach leads to a definition of iaheritance that is..

The purpose of this paper is to question some commonly accepted patterns of reasoning involving nonmonotonic logics that generate multiple extensions. In particular, I argue that the phenomenon of floating conclusions indicates a problem with the view that the skeptical consequences of such theories should be identified with the statements that are supported by each of their various extensions.

This is a title on the foundations of defeasible logic, which explores the formal properties of everyday reasoning patterns whereby people jump to conclusions, reserving the right to retract them in the light of further information. Although technical in nature the book contains sections that outline basic issues by means of intuitive and simple examples. This book is primarily targeted at philosophers interested in the foundations of defeasible logic, logicians, and specialists in artificial intelligence and theoretical computer science.

We address problems of conflicting evidence--ambiguity--in nonmonotonic reasoning. In particular, we provide a unified framework for studying such ambiguity and for identifying principles that may aid in resolving it. This framework clarifies the issues that underlie particular ambiguity problems. It unifies existing approaches by providing a common description language. And it suggests new solutions by shifting the focus to underlying principles, rather than particular procedures. We analyze three specific examples of ambiguity--in inheritance, temporal reasoning, and counterfactual reasoning--in terms of this (...) unified framework, and provide systems for reasoning about these ambiguities based on the principles of specificity, causation, and similarity of worlds. (shrink)