Reasoning with perceived information: A case for nonmonotonic reasoning

Abstract

Several nonmonotonic logics have been proposed and studied in the context of human commonsense reasoning. Commonsense reasoning involves reasoning with perceived information which is often incomplete. The existing logics can handle defeasible nonmonotonic inferences. We propose a modified first-order logic so that defeasible beliefs can also be handled. The modification is in the form of a set of proper axioms to handle belief revision, and a modified modus ponens to capture  nonmonotonic reasoning. The proposed logic provides a basis for contextual reasoning and also attempts to capture the notion of 'forgetfulness'. The proposed logic also permits property inheritance with exceptions from multiple more general concepts. The consistency of the theory generated using modified first-order logic is also examined.