What Makes A Thriller A Thriller?

Some time ago, I had a long discussion with the most prolific consumer of both fantasy and horror books (and movies) that I know, my oldest son, about just what makes “horror” horror? Or, what makes a “thriller” a thriller, and not “suspense”? And so forth.

For example, what was “Alien”? What was “Aliens”? The same? If so, why do they feel so different?

Afterwards, I decided that I needed, for own sanity, to come up with a topology. Here’s what I developed:

Suspense = supernatural antagonist of unknown origin
Mystery = mundane antagonist of known origin
Thriller = mundane antagonist of unknown origin
Horror = supernatural antagonist of known origin

Now, this is probably more useful for movies then books (where we define “horror” largely by how we are made to feel as we read, and after we’re finished). But, in both my reading and movie viewing, it has definitely helped me highlight when the author switches from one of these to another, in order to keep the audience (poor little ME) off-balance.

I dunno—I think this works.

At any rate, I think I’ll delve more in-depth into this later—just to see if I can identify what sorts of specific promises each of these sub-genres is supposed to make to the audience.

OH, and, for the record: Alien was a Mystery (dressed up like a Suspense), while Aliens was a Thriller (dressed up like a Horror). See? Now I have an entirely new way to confuse myself!