 The first kind of case can (perhaps) be dealt with by Lewis’s modified 1973 account, by finding some intermediate event d such that the surgery raises the chance of d and d in turn raises the chance of the heart attack. But it can’t deal with the second kind of case: Billy’s throw meets Lewis’s sufficient condition for chancy causation and so the modified 1973 account erroneously counts it as a cause (Menzies 1996). This is a problem that Lewis saw for his own account and never solved: his later, 2000 account of causation as ‘influence’ assumes determinism (2000: n.1; Lewis 2004a: 79–80) and so ignores the problem. Examples of both kinds have been the subject of extensive discussion in the context of both counterfactual and probabilistic theories of causation. (For discussions about how best to deal with them within theories that don’t assume determinism, see Barker 2004; Beebee 2004a; Dowe 2000, 2004; Hitchcock 2004; Kvart 2004; Noordhof 1999, 2004; Ramachandran 1997, 2004.)