Full Idea
A rather important objection to Humeanism has been that regularity is not sufficient for causation.
Clarification
'Humeanism' is the idea that causes are just constant conjunctions of events
Gist of Idea
Regularity doesn't seem sufficient for causation
Source
Stathis Psillos (Causation and Explanation [2002], Intro)
Book Reference
Psillos,Stathis: 'Causation and Explanation' [Acumen 2002], p.4
A Reaction
Obviously a crucial problem, but the Humean view can defend itself by introducing other constant conjunctions. We don't observe events in isolation, but as part of a pattern of regularities.