The Debate over the Consequence Argument 996 We also simplify here. We shall treat it as intuitive that if the metaphysical thesis of
determinism is true, it is power necessary. Moreover, we also shall gloss over a
further logical detail. The second premise of the argument we present here expresses
power necessity with respect to the truth of a material conditional: N((p&l) → f ). But,
as we have explained (Section 1.4), determinism is best thought of as a metaphysi-
cally necessary truth about the way the world is (assuming determinism is true). That
is, determinism is the thesis that □((p&l) → f ). But for present purposes, we can
understand ((p&l) → f ) as a logical consequence of the proposition □((p&l) → f ), and
then attend to power necessity with respect to this logical consequence.
7 For a thorough treatment of these issues, see Fischer (1994: chapters 2– 6 : 23–130). In
developing this section, we rely heavily on Fischer’s assessment of these issues.
8 For a helpful discussion of these two notions of ability and how they figure in ways of
resisting the Consequence Argument, see Kapitan (2002), whose treatment we rely
upon in what follows.
9 Some might express this by saying that the laws of nature “supervene” on the actually
obtaining causal facts. (To explain, if x supervenes on y, then x depends on y, but y
does not depend on x. This might in turn be captured as follows: There can be no
change in x without a change in y; but it is possible that there could be a change in y
without there being a change in x.)
10 To help place in perspective how uncontroversial this notion of a local miracle is,
think of it this way. On this compatibilist approach, under the assumption that deter-
minism is true, in this actual world, in each scenario in which a free agent acts as she
does act, a number of local miracles actually do occur! But they are only miracles rel-
ative to different laws than the ones that actually do obtain in this world. They are
merely miracles relative to laws obtaining in the possible but non- actual worlds in
which an agent acts differently than she does in this actual world.
11 For other compatibilists advancing Lewis’s basic strategy, see Horgan (1985) and
Vihvelin (2013).
12 Slote (1982), and also Daniel Dennett (1984), have suggested that the power necessity
modality has an epistemic element of the sort allegedly at work in Closure. Hence,
knowledge necessity’s modal selectivity infects the power necessity modality in a
similar manner.
13 For a range of advanced formulations and discussions, see Fischer, 1983, 1986, 1994;
Ginet, 1966, 1980, 1990; Kapitan, 2002; Lamb, 1977; McKay and Johnson, 1996;
O’Connor, 1993, 2000; van Inwagen, 1975, 1983, 2002; Widerker, 1987; Wiggins,
1973.
14 Whereas we have elected to use the notion of power necessity as defined above
(Section 4.2), van Inwagen proceeds by using the expression “has no choice about.”
The meaning of these expressions are not synonymous, but we will proceed here as if
van Inwagen’s preferred idiom and the modality he builds from it are the same as the
one we use in this chapter.
15 See note 6 above for a more careful formulation.
16 A word of caution here: In van Inwagen’s version of the argument, as we shall set out
below, the argument does not proceed from step 1 to 2 as we have set it out in this
paragraph. Instead, before applying Rule α, an intermediate logical operation is per-
formed on the way the first step is formulated. Then Rule α is applied to that formula-
tion. We’ll explain the motivation for this extra step after setting out the argument.
Note also that, strictly speaking, what follows from □((Po&L) → P) and Rule α is not
that it is power necessary that it is necessarily true that P is implied by Po&L. (Here