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Low. The hypothesis of a hollow Earth has been dismissed by the scientific community since the late 18th century, but there was a period when scientists theorized about its structure and mechanics. The science used in Hollow Earth (even when based on sound scientific principles) stories to discover, explain, and inhabit is generally speculative.

Variable. With the creation of another civilization, community, or habitable space where a community can grow, there is of course potential for social commentary and the exploration of philosophical ideas. Indeed, some authors create the world within our world to do just that.

Other Hollow Earth stories are pure adventure with an emphasis on discovery and entertainment. These types of Hollow Earth stories tend not to explore grand ideas.

Variable. There are some typical adventure types in this sub-genre and they don't have much depth. However, some stories do offer well developed characters who delve into the Earth's depths for meaningful reasons.

Moderate. Hollow Earth stories are not epic sagas, but they are a fun adventure full of discovery, which makes for an engaging plot with plenty of forward momentum.

Variable. Many stories are journeys of discovery and discovery doesn't always mean violence. Sometimes though violence erupts between differing societies—it just depends on the story.