In the discussion above I postponed addressing the problems of preemption and overdetermination as well as the difficulties raised by arbitrary event fusions and complex facts. In this chapter, I confront these problems and then end by drawing overall conclusions in which the pieces examined in the previous chapters will, I hope, find their places.

Overdetermination

Suppose an event e is causally overdetermined by two events, a and c. For example, suppose a and c are simultaneous, a involves pushing button one, which closes a circuit and causes a light to go on. c involves pushing button two, which closes the same circuit at exactly the same time and causes the same light to go on. e is the light going on. If a had not occurred, c alone would have caused e. If c had not occurred, a would have caused e. As things are, however, it is not the case that only one of a or c caused e. Either they both caused e or neither caused e. Each of them is a “causal overdeterminer” of e.

What is this relation of causal overdetermination? The most common approach in the literature, which I will endorse, denies that causal overdeterminers are causes. If a and c are causal overdeterminers of e, then neither a nor c is a cause of e. Instead one takes the instantiation of the disjunctive property, A or C at the relevant place and time as a cause of e.