 As we have seen, Lewis employs his strategy of defining causation in terms of chains of causal dependence not only to make causation transitive, but also to deal with preemption examples. However, there are preemption examples that this strategy cannot deal with satisfactorily. Difficulties concerning preemption have proven to be the biggest bugbear for Lewis’s theory. (Paul and Hall 2013: Chap. 3 contains an extensive discussion of the problems posed by preemption and other kinds of redundant causation for counterfactual theories.) 