 A second problem runs as follows. Assume, plausibly, that a giant meteor caused the dinosaurs to go extinct. For the meteor to be a cause on HRT, there must be a regularity saying that events like giant meteors hitting the Earth are followed by events like the extinction of the dinosaurs. But it seems as if such a regularity does not exist: the next giant meteor hitting the Earth will not cause the dinosaurs to go extinct. The dinosaurs are already extinct. The problem is that the meteor is only a cause of the extinction on a single occasion. But according to HRT this one meteor hitting the Earth is only a cause if some other meteors hitting the Earth also satisfy the regularity. But why would events far away in space and time determine whether or not this giant meteor caused the extinction of the dinosaurs on this occasion? It seems as if we can have causation without regularity on a single occasion. We will refer to this problem as the problem of singular causal relations.