Full Idea
Imagine a Venusian lands on Earth and observes a forest fire, and says 'I know what caused that - the atmosphere is saturated with oxygen!'. Thus one man's 'background condition' can easily be another man's 'cause'.
Gist of Idea
An alien might think oxygen was the main cause of a forest fire
Source
Hilary Putnam (Why there isn't a ready-made world [1981], 'Causation')
Book Reference
Putnam,Hilary: 'Realism and Reason: Papers vol 3' [CUP 1985], p.214
A Reaction
You can't sweep 'the' cause of a fire away so easily. There is always oxygen on Earth, but only occasional forest fires. The oxygen doesn't 'trigger' the fire (i.e. it isn't the proximate cause).