Online Papers - Brian Weatherson

David Lewis 74
parked cars influences the smashing of a window by a rock in virtue of small gravitational
effects of the cars on the flight of the rock. But it’s very little influence, and we
properly ignore it most of the time.
There are two other notable features of “Causation as Influence”. It contains
Lewis’s most comprehensive defence of the transitivity of causation. This principle
was central to Lewis’s theory of causation from the earliest days, but had come under
sustained attack over the years. And the paper has a brief attack on non-Humean
theories that take causation to be a primitive. Lewis says that these theories can’t
explain the variety of causal relations that we perceive and can think about. These
passages mark an interesting change in what Lewis took to be the primary alternatives
to his counterfactuals based reductionism. In 1973 the opponents were other kinds
of reductionists; in 2000 they were the non-reductionists.
5.3 Why Humean Supervenience
Given these concepts, a number of other concepts fall into place. Dispositions are
reduced to counterfactual dependencies, though as is made clear in “Finkish Dispositions”
(1997b), the reduction is not as simple as it might have seemed. Perception
is reduced to dispositions and causes. (See, for instance, “Veridical Hallucination and
Prosthetic Vision” (1980d).) We discussed the reduction of mental content to dispositions
and causes in section 4. And we discussed the reduction of linguistic content
to mental content in section 1. Values are reduced to mental states in “Dispositional
Theories of Value” (1989b).
But we might worry about the very foundation of the project. We started with
the assumption that our subvenient base consists of intrinsic properties of pointsized
objects and spatiotemporal relations. But Bell’s inequality suggests that modern
physics requires, as primitive, other relations between objects. (Or it requires intrinsic
properties of dispersed objects.) So Humean supervenience fails in this world.
Lewis’s response is somewhat disarming. Writing in 1986, part of his response is
scepticism about the state of quantum mechanics. (There is notably less scepticism
in “How Many Lives Has Schr odinger’s Cat” (2004b).) But the larger part of his
response is to suggest that scientific challenges to Humean supervenience are outside
his responsibility.
Really, what I uphold is not so much the truth of Humean supervenience
as the tenability of it. If physics itself were to teach me that it is false,
I wouldn’t grieve ... What I want to fight are philosophical arguments
against Humean supervenience. When philosophers claim that one or
another common-place feature of the world cannot supervene on the arrangement
of qualities, I make it my business to resist. Being a commonsensical
fellow (except where unactualized possible worlds are concerned)
I will seldom deny that the features in question exist. I grant their existence,
and do my best to show how they can, after all, supervene on the
arrangement of qualities. (1986c, xi)