Even while staying at the clean, well-lighted café, the old man sits “in the shadow” of the trees. The shadow represents his depression and despair that never leaves him. Shadow is where light meets darkness, and they mingle. From this point of view, it symbolizes the transition from life to death, from existence to nothingness.
The author repeatedly mentions that the café visitor sits in the shadow of the trees. Meanwhile, the site is well-lighted. Why should he strive to stay at an illuminated place but prefer sitting in the shadow?
The man is about eighty, as the waiters mention. He is well-to-do but lonely, deaf, and depressed. In a word, the old man is as unhappy as a person may be. In the short story, light represents everything positive in life. But all those pleasures (communication, love, motivation, etc.) are unattainable for him. He can only watch the light from the shadow.
The recurring picture of “the old man sitting in the shadow” means the depth of his loneliness and separation from real life. His deafness intensifies this image. The man “liked to sit late because he was deaf and now at night it was quiet and he felt the difference.” He is deaf to people, but he does not hear the world either. The older waiter can relate to this. He knows all the emptiness of living on a deserted planet.