Full Idea
Causal relations cannot be reduced to mere regularities, as Hume supposed, as they could exist as a singular case, even if it never happened on more than one occasions.
Gist of Idea
Causal relations cannot be reduced to regularities, as they could occur just once
Source
Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.3)
Book Reference
Ellis,Brian: 'The Philosophy of Nature: new essentialism' [Acumen 2002], p.49
A Reaction
This seems to be the key reason for modern views moving away from Hume. The suspicion is that regularity is a test for or symptom of causation, but we are deeply committed to the real nature of causation being whatever creates the regularities.