The author talks about absence and memory and how "We can miss things we have known and lost, things that never were but that are imagined. We can miss things that we once had or people we once knew and we can miss things that never existed or that have never been a part of our lives". He talks about visiting Ground Zero in New York "where the absence of everything was overwhelming. ... . The people standing near me were silent, thoughtful, seeing something, perhaps, totally different from what I was seeing. Minds filling in what the eyes could not see. And missing things that had been, people who had been".