Online Papers - Brian Weatherson

David Lewis 72
5.2 Causation
In “Causation” (1973a), Lewis put forward an analysis of causation in terms of counterfactual
dependence. The idea was that event B was counterfactually dependent on
event A if and only if the counterfactual Had A not occurred, B would not have occurred
was true. Then event C causes event E if and only if there is a chain C, D 1 ,
..., D n , E such that each member in the chain (except C) is counterfactually dependent
on the event before it. In summary, causation is the ancestral of counterfactual
dependence.
The reasoning about chains helped Lewis sidestep a problem that many thought
unavoidable for a counterfactual theory of causation, namely the problem of preempting
causes. Imagine that Suzy throws a rock, the rock hits a window and the
window shatters. Suzy’s throw caused the window to shatter. But there is a backup
thrower—Billy. Had Suzy not thrown, Billy would have thrown another rock and
broken the window. So the window breaking is not counterfactually dependent on
Suzy’s throw. Lewis’s solution was to posit an event of the rock flying towards the
window. Had Suzy not thrown, the rock would not have been flying towards the
window. And had the rock not been flying towards the window, the window would
have not shattered. Lewis’s thought here is that it is Suzy’s throwing that causes
Billy to not throw; once she has thrown Billy is out of the picture and the window’s
shattering depends only on what Suzy’s rock does. So we avoid this problem of preempters.
Much of the argumentation in “Causation” concerns the superiority of the counterfactual
analysis to deductive-nomological theories. These arguments were so successful
that from a contemporary perspective they seem somewhat quaint. There are
so few supporters of deductive-nomological theories in contemporary metaphysics
that a modern paper would not spend nearly so much time on them.
After “Causation” the focus, at least of those interested in reductive theories,
moved to counterfactual theories. And it became clear that Lewis had a bit of work
left to do. He needed to say more about the details of the notion of counterfactual dependence.
He did this in “Counterfactual Dependence and Time’s Arrow” (1979b), as
discussed in section 2. He needed to say more about the nature of events. In “Events”
(1986a) he said that they were natural properties of regions of space-time. And prodded
by Jaegwon Kim (1973), he needed to add that A and B had to be wholly distinct
events for B to counterfactually depend on A. The alternative would be to say that an
event’s happening is caused by any essential part of the event, which is absurd.
But the biggest problem concerned what became known as “late pre-emption”. In
the rock throwing example above, we assumed that Billy decided not to throw when
he saw Suzy throwing. But we can imagine a variant of the case where Billy waits to
see whether Suzy’s rock hits, and only then decides not to throw. In such a case, it
is the window’s shattering, not anything prior to this, that causes Billy not to throw.
That means that there is no event between Suzy’s throw and the window’s shattering
on which the shattering is counterfactually dependent.
Lewis addressed this issue in “Redundant Causation”, one of the six postscripts to
the reprinting of “Causation” in (1986c). He started by introducing a new concept: