Full Idea
In Mill's 'Method of Difference' the cause is the factor which is different in two cases which are similar, except that in one the effect occurs, and in the other it doesn't.
Gist of Idea
In Mill's 'Method of Difference' the cause is what stops the effect when it is removed
Source
report of John Stuart Mill (System of Logic [1843], p.256) by Stathis Psillos - Causation and Explanation §2.3
Book Reference
Psillos,Stathis: 'Causation and Explanation' [Acumen 2002], p.64
A Reaction
Like the Method of Agreement, this is a good test, but is unlikely to be a conclusive hallmark of causation. A footballer may never score unless I go to watch him. I become his lucky mascot…