I hesitate to predict whether this theory is true. But if the general opinion of Mankind is optimistic then we’re in for a period of extreme popularity for science fiction.

Eddings frames science fiction’s popularity as responsive to collective mood rather than purely to literary fashion. The remark suggests a “theory” (left unspecified here) that when people feel broadly hopeful about the future—technologically, socially, or politically—they are more receptive to speculative narratives that imagine new worlds, progress, and possibility. Conversely, if public sentiment turns pessimistic, readers may gravitate toward genres that emphasize decline, horror, or nostalgia. The quote also carries a self-aware caution: he refuses to assert the theory as fact, but uses it to predict market cycles, implying that genre success can be read as a barometer of cultural optimism.