Full Idea
If causation involves any kind of necessity, it should survive the test of antecedent strengthening. ...It is plausible that for any type of causal process, that some new cause can be added which typically results in the effect no longer being caused.
Gist of Idea
Necessary causation should survive antecedent strengthening, but no cause can always survive that
Source
S.Mumford/R.Lill Anjum (Getting Causes from Powers [2011], 3.5)
Book Reference
Anjum,R.J./Mumford,S.: 'Getting Causes from Powers' [OUP 2011], p.56
A Reaction
[Idea expanded p.57] This is their key argument against the idea that causation involves necessity. In simple terms, show me a cause which necessarily leads to some result, and I will show you how you could prevent that result. Sounds good.