Full Idea
A cause is the sum total of the conditions positive and negative taken together ...which being realized, the consequent invariably follows.
Gist of Idea
A cause is the total of all the conditions which inevitably produce the result
Source
John Stuart Mill (System of Logic [1843]), quoted by Donald Davidson - Causal Relations §1
Book Reference
Davidson,Donald: 'Essays on Actions and Events' [OUP 1982], p.150
A Reaction
This has obvious problems. The absence of Napoleon was a cause of the English Civil War. The Big Bang was a cause of, well, every event. As Davidson notes, some narrowing down is needed.