The late neurologist and author Oliver Sacks wrote about a patient who, he said, remembered everything. He could recall anything at any distance in time. But that's not possible for the simple reason that we consciously experience only about 5% of what comes in through our senses. So, the most he could possibly bring back is a tiny fraction of any moment or isolated scene. But that got me thinking about what we remember and what we forget. Who decides? How? Most important, why?