In Hemingway's iconography, good places are clean and filled with light. We see this in "The Snows of Kilimanjaro," as well, when Harry dreams he is taken to the mountaintop, where he is at peace, as he actually lies dying in the valley, filled with self-recrimination. In this story, the cafe is clean and well lit, while outside, the dark descends. The older waiter muses on this as he closes the cafe: "It was only that and light was all it needed and a certain cleanness and order." The young waiter had been impatient to return to his home and his wife, while the older waiter, who suffers from insomnia, wants to linger in the cafe, reflecting on his life and his emptiness. This older waiter has also displayed sympathy for the customer who had tried to kill himself.

In Modernist literature, and in Hemingway especially, it's important to listen for echoes of earlier works—the collective memories of a culture that seems to have faded. In this brief interlude, the old waiter's thoughts of suicide and his inability to sleep may well be an echo of Hamlet's "To be, or not to be soliloquy," where sleep and death are also equated:

To die, to sleep;
No more; and by a sleep to say we end
The heart-ache and the thousand natural shocks
That flesh is heir to, 'tis a consummation
Devoutly to be wish'd. To die, to sleep;
To sleep: perchance to dream: ay, there's the rub:
For in that sleep of death what dreams may come
When we have shuffled off this mortal coil,
Must give us pause; there's the respect
That makes calamity of so long life . . .

The insomnia seems to relate to the Modernist ennui and despair that is so much a part of Existentialism. The nada prayer is the cry of a soul seeking meaning in an apparently meaningless world. The insomnia is the fear to end that long life.

Insomnia in "A Clean, Well-Lighted Place" is indicative of the feeling of hopelessness or disillusion that the older waiter is feeling about life.

He dismisses this disillusion as "insomnia," but it represents more than that. The older waiter seems to be of the generation who saw the worst of The Great War (World War I) and dismisses this disillusion about life as this disorder and says "many must have it."

So how does the reader know that the older waiter suffers from disillusion, or nothingness? Two reasons:

1. His empathy for the old man who tried to kill himself. As characters, the older waiter is much more like the old man than the younger waiter. The old man has no one except for a niece and his suicide attempt was a way for him to end his feelings of nothingness.
2. The prayer. The older waiter replaces many words in "The Lord's Prayer" with the word "nada" (Spanish for "nothing"). This suggests that Catholicism and religion as a whole, which is what many used to replace a feeling of disillusion, no longer satiated people.

It's important to remember that diseases and disorders in fiction are chosen very carefully. Insomnia is very symbolic in that it prevents sleep, which is a way for people to shut out the bad things, at least for a little time. For the older waiter, the bad things can never be shut out.