Full Idea
An early view of causation (Mill and Hume) is whatever is (ceteris paribus) sufficient for the event. A second view (E.Nagel) is that the cause should just be necessary. Some (R.Taylor) even contemplate the cause having to be necessary and sufficient.
Clarification
'Ceteris paribus' (L) means 'all things being equal'
Gist of Idea
Are causes sufficient for the event, or necessary, or both?
Source
E Sosa / M Tooley (Introduction to 'Causation' [1993], §2)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.6
A Reaction
A cause can't be necessary if there is some other way to achieve the effect. A single cause is not sufficient if many other factors are also essential. If neither of those is right, then 'both' is wrong. Enter John Mackie...