The second essay in The Weight of Glory speaks to how Christians should act and what Christians ought to care about even in times of desperation like war. In short, Lewis encourages us to not lose sight of eternity.
Humanity, he says, has always had a shadow of "something infinitely more important than itself." This provides a curiosity to explore and search out the unknown. Lewis argues that during wartime, the principle of an all-absorbing focus is brought to bear at least for those moments engaged in conflict. The religious life is kin to a wartime intensity but it replaces everything. Lewis says that our natural life becomes, "a new organization which exploits, to its own supernatural ends, these natural materials."
Certainly our lives are made of seemingly mundane days for the most part, but God reorders the Christian to live a life "as to the Lord" no matter if it be the work of Beethoven or that of a maid. With such realization comes humility, and likened to war, we must be patient, fearless and able to recognize the larger mission at work.
Lewis, who fought in the first World War and lived through the second, reminds us at the close of the chapter of an important lesson about wartime, perhaps the most important lesson. "If we had foolish un-Christian hopes about human culture," he says, "they are now shattered. If we thought we were building up a heaven on earth, if we looked for something that would turn the present world from a place of pilgrimage into a permanent city satisfying the soul of man, we are disillusioned, and not a moment too soon."