Online Papers - Brian Weatherson

David Lewis 60
getting us closer to actuality if we’ve added a big miracle. So in fact the nearest worlds
are ones where a nuclear war occurs, and (3.5) is true.
One way to see the effects of Lewis’s ordering is to work through its implication
for an important class of cases. When the antecedent of a counterfactual is about
the occurrence or non-occurrence of a particular event E at time t, the effect of these
rules is to say that the nearest worlds are the worlds where the following claims all
hold, with t* being as late as possible.
• There is an exact match of particular fact with actuality up to t*.
• There is a small, localized law violation at t*.
• There is exact conformity to the laws of actuality after t*.
• The antecedent is true.
So we find a point just before t where we can make the antecedent true by making
a small law violation, and let the laws take over from there. There is something
intuitively plausible about this way of viewing counterfactuals; often we do aim to
talk about what would have happened if things had gone on in accordance with the
laws, given a starting point slightly different from the one that actually obtained.
Jonathan Bennett (2003) notes that when the antecedent of a conditional is not
about a particular event, Lewis’s conditions provide the wrong results. For instance,
if the antecedent is of the form If one of these events had not happened, then Lewis’s
rules say that the nearest world where the antecedent is true is always the world where
the most recent such event did not happen. But this does not seem to provide intuitively
correct truth conditions for such conditionals. This need not bother Lewis’s
larger project. For one thing, Lewis was not committed to there being a uniform
similarity metric for all counterfactuals. Lewis could say that his default metric was
only meant to apply to cases where the antecedent was about the happening or nonhappening
of a particular event at a particular time, and it wouldn’t have seriously
undermined his larger project. Indeed, as we’ll see in Section 5.2 below, the counterfactuals
he was most interested in, and for which these criteria of similarity were
devised, did have antecedents concerning specific events.
4 Philosophy of Mind
In “Reduction of Mind” (1994b), David Lewis separates his contributions to philosophy
of mind into two broad categories. The first category is his reductionist metaphysics.
From his first published philosophy paper, “An Argument for the Identity
Theory” (1966), Lewis defended a version of the mind-brain identity theory (see the
entry on the identity theory of mind). As he makes clear in “Reduction of Mind”,
this became an important part of his global reductionism. We’ll look at his metaphysics
of mind in sections 4.1–4.3.
The second category is his interpretationist theory of mental content. Following
Donald Davidson in broad outlines, Lewis held that the contents of a person’s mental
states are those contents that a radical interpreter would interpret them as having,
assuming the interpreter went about their task in the right way. Lewis had some