got a little self-conscious. I said: "I guess it's sort of futile trying to keep a backup file of my personal memories..."

he said: "Not at all...because we use so many machines, it's not surprising we should store memories there, as well as in our bodies. The one thing that differentiates human beings from all other creatures on Earth is the externalization of subjective memory—first through notches in trees, then through cave paintings, then through the written word and now, through databases of almost otherworldly storage and retrieval power."