Abstract

This is a study of a problem in the logic of belief revision. On the assumption of a number of fairly traditional views concerning the relationship between mind and world, the mechanics of perception, and the nature of belief, an argument is made to the effect that revision of extant beliefs is impossible even in the light of new perceptual experience. The argument turns on the ability of a cognitive system to recognize conflict among its thoughts and perceptions. A number of models of the mechanics of perceptual interpretation are explored, all of which are revealed to share a susceptibility to the problem as posed. Certain objections are taken up, the responses to which modify the scope of the original argument; although the problem may yet be said to arise in a number of crucial contexts where its presence is undesirable, some situations are found in which the problem can be dissolved. The problem is then reexamined in light of the epistemological position called fallibilism, with an eye to demonstrating that it arises notwithstanding the highly cautious perspective embodied in that position. A solution to the problem is then offered in the form of a family of model cognitive systems with certain properties. Because the problem is a feature of belief-based cognitive systems, the family of systems offered in arguing for a resolution of the problem is constructed on the notion that cognition, construed as information processing, normally proceeds without any epistemic evaluations being attached either to perceptions in particular or thoughts in general. The non-evaluative propositional attitude employed in normal cognition should, I argue, be what I call acceptance. The propositional attitude of belief, traditionally conceived of as occupying the role now given to acceptance, is accorded an extremely limited scope of application. Epistemic evaluation in general is itself restricted to contexts of decision only, its application arising only.