Humeans Aren't Out of their Minds

Humeanism is “the thesis that the whole truth about a world like ours supervenes on the spatiotemporal distribution of local qualities.” (Lewis, 1994, 473) Since the whole truth about our world contains truths about causation, causation must be located in the mosaic of local qualities that the Humean says constitute the whole truth about the world. The most natural ways to do this involve causation being in some sense extrinsic. To take the simplest possible Humean analysis, we might say that c causes e iff throughout the mosaic events of the same type as c are usually followed by events of type e. For short, the causal relation is the constant conjunction relation. Whether this obtains is determined by the mosaic, so this is a Humean theory, but it isn’t determined just by c and e themselves, so whether c causes e is extrinsic to the pair. Now this is obviously a bad theory of causation, but the fact that causation is extrinsic is retained even by good Humean theories of causation. John Hawthorne (2004) objects to this feature of Humeanism. I’m going to argue that his arguments don’t work, but first we need to clear up three preliminaries about causation and intrinsicness. First, my wording so far has been cagey because I haven’t wanted to say that Humeans typically take causation to be an extrinsic relation. That’s because the greatest Humean of them all, David Lewis, denies that causation is a relation at all, and hence that it is an extrinsic relation (Lewis, 2004b). We can go some way to avoiding this complication by talking, as Hawthorne does, about properties of regions, and asking the property of containing a duplicate of c that causes a duplicate of e is intrinsic or extrinsic.1 Humeans typically take causation to be extrinsic in this sense. Second, nothing in Humeanism requires that causation is extrinsic in that sense. If one analysed causation as that intrinsic relation that actually most tightly correlates with the constant conjunction relation, then one would have guaranteed that causation was an intrinsic relation. Moreover, one would have a perfectly Humean theory of causation. (A perfectly awful theory, to be sure, but still a Humean one.) Peter Menzies (1996, 1999) develops a more sophisticated version of such a theory, and though Menzies describes his view as anti-Humean, one can locate the relation we’ve defined here in the Humean mosaic, so such an approach might be consistent with Humeanism in the intended sense. Third, there is good reason, independent of Humeanism, to accept that causation is extrinsic. As Ned Hall (2004) argues, it is very hard to square the intrinsicness of causation with the possibility of causation by omission. Given the choice between