Defeasible Reasoning and Representation

Abstract

The Gettier Problem exhibits how our human cognitive fallibility of representation noted by Sellars and Quine always leaves open the possibility of completely justified beliefs being false. True justified belief, Gettier showed us, may result from the deduction of a justified false belief and thus fall short of knowledge. Justification that yields knowledge must not depend essentially on any error in the background system of the subject that defeats or refutes the justification. The justification consists of the capacity to meet objections to defend the target claim on the basis of acceptances, preferences over acceptances, and reasonings with acceptances contained in the background system of the subject. Errors in the system consist of accepting something false, preferring a false acceptance, or unsound reasonings. Knowledge is a kind of coherence based on defensibility of the target claim that is undefeated by errors and irrefutable by corrections of such errors.