Comparing atheism and theism in an analogy

Imagine you wake up in an enormous cavern that is deep underground that seems to extend on forever in every direction with a river that runs through the center of the cavern which comes from a hole in the rock and exits through a hole in the rock. There is also a large pool. Glowing edible fungus provides subsistence and light sufficient to see in dim shades of gray. You have no memory of any other condition besides than the one that you are now in. As you wander around you meet many people who have different perspectives about life here. You also discover that almost everywhere there are books that talk about a place some call: "The great expanse". They talk the great expanse being full of strange plants, bright light and things appearing in alternate shades besides gray (which didn't really even make sense, since you have no concept of color). Some of it sounds very odd and incomprehensible. A large group of people are actively digging upward to try to get to t...