Counterfactuals

Abstract

Counterfactuals arc a form of commonsense non-monotonic inference that has been of long- term interest to philosophers. In this paper, we begin by dc~cribing some of the impact connterfact:uals can he expcct(!d to have in artificia l intelligence, and by reviewing briefly some of the philosophical conclusions which have been drawn about them. Philosophers have noted that the content of any particular connterfactual is in part context-dependent; we present a formal rlescription of counterfactuals that is formally idcutical to the "possib le worlds" interpretation due to David Lewis and which allows us to eDcod·e this contextdependent information clearly in the choice of a sub lmi.g1mge of the logical language in which we are working. Finally, we examine the app lication of our ideas in the domain of automated diagnosis of hardware faults.