"Wecan de???ne a positive fact in W as one that holds in every world that contains W as a properpart;16 a positive property is one that if instantiated in a world W , is also instantiated bythe corresponding individual in all worlds that contain W as a proper part.17 Most everydayfacts and properties are positive???think of the property of being a kangaroo, or of being sixfeet tall, or of having a" . . . .