A poor thesis statement about H. P. Lovecraft's Dagon would be:
<em>Dagon is about the fear of being lost</em>
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This is a poor statement because, even though the main character of the story is actually lost and is not sure how he ended up in that weird place, the story is about so much more than that and it involves the unknown, the incomprehensible, and intelligent beings that only reveal the insignificance of the human race. Dagon makes you feel lost, but not as if you didn't know where you where, but more like as if nothing around you makes sense. You're not lost in a place on Earth, you're lost in the whole Universe. It's not a special fear, but an internal fear of not knowing what matters when you realize your place in the infinite universe: a place of insignificance.
The primary attribute of the characters in morality plays reflects the fact that these plays were naive allegories is the fact that the characters are often very simplified.