Causation as Influence

David Lewis
2000 Journal of Philosophy  
Ihave long advocated a counterfactual analysis of causation. But the simplest counterfactual analysis breaks down in cases of redundant causation, wherefore we need extra bells and whistles. I have changed my mind once more about how those bells and whistles ought to work.' I. PREEMPTION REVISITED It sometimes happens that two separate potential causes for a certain effect are both present; and either one by itself would have been followed by the effect; and so the effect depends upon neither.
more » ... ends upon neither. Call any such situation a case of redundant causation. Some cases of redundancy are symmetrical: both candidates have an equal claim to be called causes of the effect. Nothing, either obvious or hidden, breaks the tie between them. It may be unclear whether to say that each is a cause or whether to say that neither is a cause (in which case we can still say that the combination of the two is a cause). But, anyway, it is out of the question to say that one is a cause and the other is not. Because it is unclear what we want to say, these symmetrical cases are not effective test cases for proposed analyses of causation. Set them aside. Other cases are asymmetrical. It is very clear what we want to say: one of the two potential causes did cause the effect, the other one did not. Call the one that did a preempting cause of the effect; call the other one a preempted alternative, or backup. When our opinions are clear, it is incumbent on an analysis of causation to get them right. This turns out to be a severe test. The simplest sort of deductive-nomological analysis flunks: the preempted alternative is a member of a minimal set of conditions lawfully sufficient for the effect, yet it is not a cause. The simplest sort of counterfactual analysis likewise flunks: the preempting cause is not a condition without which the effect would have been absent, yet it is a cause. Both these attempts fail because they treat the preempting , , and the Boyce Gibson Memorial Library. I Here I shall confine my attention to causation under deterministic laws. More likely than not, causation in the actual world requires a probabilistic analysis, but that raises problems independent of those I shall be discussing. 0022-362X/00/9704/182-97 ? 2000 The Journal of Philosophy, Inc. CAUSATION AS INFLUENCE cause and its preempted alternative alike, whereas we know very well that one is a cause and the other is not. A correct analysis will need to discern the source of the difference. II. TRUMPING I used to think that all cases of preemption were cases of cutting: cases in which, first, there is a completed causal chain running from the preempting cause all the way to the effect; but, second, something cuts short the potential alternative causal chain that would, in the absence of the preempting cause, have run from the preempted alternative to the effect. Some think so still, but I have learned better.2 The sergeant and the major are shouting orders at the soldiers. The soldiers know that in case of conflict, they must obey the superior officer. But as it happens, there is no conflict. Sergeant and major simultaneously shout 'Advance!'; the soldiers hear them both; the soldiers advance. Their advancing is redundantly caused: if the sergeant had shouted 'Advance!' and the major had been silent, or if the major had shouted 'Advance!' and the sergeant had been silent, the soldiers would still have advanced. But the redundancy is asymmetrical: since the soldiers obey the superior officer, they advance because the major orders them to, not because the sergeant does. The major preempts the sergeant in causing them to advance. The major's order trumps the sergeant's. 3 We can speculate that this might be a case of cutting. Maybe when a soldier hears the major giving orders, this places a block somewhere in his brain, so that the signal coming from the sergeant gets stopped before it gets as far as it would have if the major had been silent and the sergeant had been obeyed. Maybe so. Or maybe not. We do not know one way or the other. It is epistemically possible, and hence it is possible simpliciter, that this is a case of preemption without cutting.
doi:10.2307/2678389 fatcat:vkcltoao6rc7zlqqfvy4ize5mu