On the difference between a thriller and a horror film as experienced in the body.

The theoretical distinction between thriller and horror is about the kind of threat: external/comprehensible versus internal/incomprehensible. The phenomenological distinction is about where in the body you feel the film.

Thrillers are felt in the chest: the elevated heart rate of anticipation, the release of resolution. The pleasure is physiological and it's controlled: you can feel the manipulation of your responses as it happens, and the feeling of being manipulated is part of the pleasure.

Horror is felt differently and less controllably. The best horror films produce sensations that the audience cannot entirely manage with rational film-watching strategies. The revulsion is real revulsion. The dread is real dread. The viewer cannot step back from it the way they can step back from a thriller.

This is why horror is the most intimate genre and the most difficult to describe to people who haven't felt it. You cannot explain why Hereditary is more frightening than any thriller by describing its plot or its technique. You have to convey what it feels like to be in the theater when Ari Aster springs what he springs in the first half, and that feeling is specifically physical.