 Convinced by the need to make room in his analysis for causation by (and of) absence – as when the gardener’s failure to water the plants causes their death – Lewis later amended his view to the view that causal dependence is a matter of counterfactual dependence between events or their absences (Lewis 2000: §X; 2004b). We shall largely ignore this complication in what follows; for some discussion of causation by absence see Schaffer 2000b, Beebee 2004b, McGrath 2005, Livengood and Machery 2007, Dowe 2009.