# exclusion.pdf - Causal Closure and the Exclusion Argument...

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Causal Closure and the Exclusion Argument Gabriel Greenberg (UCLA), February 2, 2019 The Exclusion Argument is one of the main arguments for physicalism, and against interactionist dualism. In this note, I’ll explain the argument, provide some background about causation, and elaborate on the key premises. 1 Causation The Exclusion Argument is all about causation, so we’ll first have to get clear about a few back- ground assumptions having to do with the structure of causation. To begin, it is widely assumed that all physical events (except perhaps for the beginning of the universe) have causes. In fact, nearly all physical events have many causes. Take the recent wild- fires in Los Angeles. Why did this event occur? One cause was (let’s imagine) a sparking power line. Another cause was the dryness of the wood in the area, itself caused by prolonged drought. Perhaps a third cause was the lack of rain during the time of the fire. And so on. Let us call these different factors PARTIAL CAUSES . They are causes of the wildfire. But they are only partial , because none of them alone would have been enough to bring about the fire. For example, if the forest had been wet, the sparking power line would not have been enough to cause the fire. Although each partial cause alone is insufficient to lead to fire, all the partial causes together are sufficient. In fact, we can collect these many partial causes together into a giant bundle of events. I’ll call this bundle of events a FULL CAUSE . Let us define the full cause of an event as any collection of partial causes which together are sufficient to bring about that event. Some authors use the term “sufficient cause” for the same idea. While most large-scale events have many partial causes (like the wildfire), it is rare for an event to have more than one full cause. When an event has more than one full cause, we call it a case of OVERDETERMINATION . Overdetermination occurs only in unusual or coincidental situations. Take the case of two assassins who both shoot the same target in the heart, at the same time, but from different positions. Both shots would have killed the target on their own, so both shots are full causes. Yet clearly this is abnormal case; most events are not overdetermined. The point for now, is not to confuse an event having multiple partial causes, which is normal, with an event having multiple full causes, which is highly unusual. §1 Causation 1
2 Causal closure The causal closure of physics is the idea that every physical event has a full (or sufficient) cause, and that this cause is itself physical. Crane (2001, 45) puts it this way: “Every physical event has a physical cause which is enough to bring it about, given the laws of physics.” The idea is captured well by Papineau (not part of the original reading): At first pass the causal closure of physics says that every physical effect has a sufficient physical cause... If you consider any physical effect, then there will arguably always