 Lewis himself takes this latter, invariantist approach (Lewis 2004b). The causes of any given event are many and varied, and in any given explanatory context most of them fail to be salient; that is why it strikes us as wrong to mention them (Lewis 1986d). Lewis’s approach is to explain (some of) the phenomena that motivate contextualism by appealing to a broadly Gricean story about conversational implicature. An advantage of invariantism is that it allows us to conceive of causation as a fully objective, mind-independent – or, as Menzies (2009: 342) puts it, a ‘natural’ – relation.