Nicholas Asher and Robert Koons
Our paper gives a unified treatment of belief change and intention revision within a dynamic logic of belief and intention. Another feature of our approach is that we distinguish hard (incorrigible, unrevisable) belief and soft belief, hard commitment and soft intention; further, the soft attitudes supervene on the hard level. We use a specific theory of nonmonotonic inference to generate soft attitudes from hard ones. This last point is especially important in attempting to deal with belief change, because when an agent acquires new beliefs there is the question: what beliefs about the world persist? We think that only a nonmonotonic logic can adequately deal with this question in a sufficiently rich framework for belief revision like the one we propose.