In Memory of Ray Reiter (1939-2002)

He leaves a legacy of groundbreaking, deep insights that have changed the course of AI. "Only one same reason is shared by all of us: we wish to create worlds as real as, but other than the world that is." The quotation captures what was special about Ray: He had an adventurer's desire to go beyond the boundaries of our current understanding, together with a mathematician's insistence on precision. Ray the adventurer was always eager to try new ideas and directions. He was not afraid to enter murky areas, and he always left them better illuminated. He introduced terms to the AI community such as default logic, closed-world assumption, and cognitive robotics; he opened avenues of theoretical research with new resolution proof methods and logics for nonmonotonic reasoning, diagnosis, and action; and he was the prime mover in the Cognitive Robotics initiative that has led to a whole new program of research.