C. S. Lewis's words from his classic essay “Learning in War-Time," written during World War II, captured some of the powerful effect 9/11 had on those of us living half a century later.

There is no question of death or life for any of us, only a question of this death or of that — of a machine gun bullet now or a cancer forty years later. 

What does war do to death? It certainly does not make it more frequent; 100 percent of us die, and the percentage cannot be increased. It puts several deaths earlier, but I hardly suppose that that is what we fear. Certainly when the moment comes, it will make little difference how many years we have behind us. 

Does it increase our chances of a painful death? I doubt it. As far as I can find out, what we call natural death is usually preceded by suffering, and a battlefield is one of the very few places where one has a reasonable prospect of dying with no pain at all. 

Does it decrease our chances of dying at peace with God? I cannot believe it. If active service does not persuade a man to prepare for death, what conceivable concatenation of circumstances would? 

Yet war does do something to death. It forces us to remember it. 

The only reason why the cancer at sixty or the paralysis at seventy-five do not bother us is that we forget them. War makes death real to us, and that would have been regarded as one of its blessings by most of the great Christians of the past. They thought it good for us to be always aware of our mortality. I am inclined to think they were right. 

All the animal life in us, all schemes of happiness that centred in this world, were always doomed to a final frustration. In ordinary times only a wise man can realize it. Now the stupidest of us knows. 

We see unmistakably the sort of universe in which we have all along been living, and must come to terms with it.

The Weight of Glory: And Other Addresses  [New York: HarperCollins, 1949], 61-62, paragraphing added.