6* - Independence and Counterfactual Dependence

Summary

After briefly discussing two other counterfactual theories of causation, this chapter formulates the account of similarity among possible worlds employed in chapter 6 and proves the claims it makes.

Mackie's Counterfactual Theory

John Mackie argued,

if on a particular occasion A's doing X is causally related to B's doing Y, and if they had not been so related but things had otherwise been as far as possible as they were, A would still have been doing X but B would (or might) not have been doing Y, then /Ts doing X is conditionally and causally prior to ZTs doing Y. (1979, p. 24)

For example, suppose one breaks the connection between a car's engine and its wheels: the engine continues turning while the wheels stop.

Let us call the event of A's doing X on the particular occasion “a” and the event of B's doing Y on the occasion “b” Suppose that in the closest possible world in which some event c failed to occur, a would not be causally connected to b. If the causal connection between a and b depends on the existence of c, then c must be a cause of at least one of a or b. On Mackie's view a is causally prior to b if and only if, in the absence of some minimal difference c, a still occurs, but b does not (B does not do Y). So c causes b only. Mackie thus indirectly assumes that there are causes of b that are not causes of a, and this assumption is, of course, an immediate implication of both CP and agency views.