There are two kinds of horror stories: experiments about mad scientists and ferocious monsters. In the horror stories about monsters, monsters symbolize the psychological confusion of the protagonist. The horror stories about mad scientists typically express the author's feelings: scientific knowledge alone is not enough to guide human exploration. Despite these differences, these two types of horror stories have the following characteristics in common: they describe phenomena that go against the laws of nature: they both want to frighten the reader.
Some stories that use symbolism describe phenomena that go against the laws of nature must be true if the above statement is true.