Do Computers Need Common Sense?

My aim in this paper is to make and defend three claims. First, it is incumbent on the knowledge representation and nonmonotonic communities to demonstrate that their ideas will eventually lead to improvements in the performance of implemented systems. Second , a reasonable working deenition of \com-monsense" reasoning is that it is the process of using polynomial techniques to convert a large instance of an NP-hard problem to a smaller instance on which search techniques can be applied eeectively. And nally, it is a consequence of these rst two claims that the most pressing problem facing the com-monsense community is the identiication of realistic problems and problem structures for which commonsense reductions are both necessary and eeective.