Darkness and Light

The whole story is built around the concepts of darkness and light. On a planet with perpetual sunlight, darkness is inconceivable. The story presents an interesting theory about the effects of darkness on a people who have never experienced it. Asimov's editor believed that such people would go mad in darkness, even though the stars would become visible. So, Asimov wrote a story based on that supposition.

Deprivation and Need

Being deprived of light is the worst fear of the people of Lagash. After 2,000 years of light, they are genetically in need of light. Darkness is an unthinkably terrifying concept. Thus, the conflict in the story is the problem of how to respond to a crisis when one of the most basic needs of existence disappears. Cleverly, Asimov provides a psychologist as one of the main characters in the story in order to discuss and analyze...