What's wrong with canberra-planning causation?
If you're asked to explain how your preferred theory of everything -- that is, your brand of physicalism -- can accomodate some entity X, the first thing to try is the Canberra Plan. It goes as follows: First, collect features that could be said to characterise X. If you're lazy, simply collect everything the folk says about X. Next, say that since these features comprise the essence of X, whatever physical entity has (more or less exactly) those features is X. Finally, explain that of course there is such a physical entity, since otherwise statements about X wouldn't be true.
Peter Menzies once applied the Canberra Plan to causation, analysing causation as whatever physical relation does this and that.
David Lewis, the chief Canberra Planner, rejected this attempt, because, he said, it faces two objections: The missing relata objection and the miscellany objection. (In fact there will turn out to be two miscellany objections.)
The missing relata objection is that absence of oxygene can cause death, even though there is no such thing as an absence of oxygene. In such cases there is no cause. And if there is causation without a cause, then causation is not a relation. So it can't be identified with whatever physical relation does this and that.
Lewis ('Void and Object') describes how this objection could be surmounted by defining causation piecemeal:
1) Event c directly causes event e iff c stand in the this-and-that-relation to e.
2) The absence of a C-event directly causes e iff, had there been a C-event, e would not have occurred.
Three more clauses are needed to deal with all kinds of causation.
Well, what is wrong with this? If we spell out 'the this-and-that-relation' as 'the influence-relation', what we get looks very much like Lewis' own account. (As I complained a while ago, his own account is stated in such a way that it is very hard to figure out what exactly it says about causation of and by absences. To me, the present account seems to be at least a good precisification of Lewis' statements.)
He says that what's wrong is that this concept of causation is too disjunctive: 'Why', he asks, 'is the disjunction of just this long list of alternatives anything more than a miscellaneous gerrymander?' This is the first miscellany objection. (Note that it is a consequence of the missing relata objection.) -- It can be answered easily: The 'long' list has five items, and these items fit together quite naturally.
In another paper (the long version of 'Causation as Influence'), Lewis seems to have a different miscellany objection in mind. Here he claims that 'causal relations are many and various' since causation between billiard balls is a different relation than causation between food and blood sugar. But why is this an objection to the Canberra Plan? After all, the Canberra Planner's analysis does say what all those relations have in common: they all occupy the this-and-that-role.