Theism and Explanation - Appeared-to-Blogly

Successful Theistic Explanations 123
competitors. This means, he argues, that they are untestable. And if they
are untestable, then they fail to meet the standards of at least a scientifi c
explanation. If this were true, it would be a conclusion which the atheist
would welcome. On the assumption that testability is at least a highly desirable
feature of any theory (scientifi c or otherwise), Sober’s argument would
practically eliminate a whole class of proposed theistic explanations at a
single stroke. But is Sober correct?
Elliot Sober’s argument. As we have seen (5.1.1), Sober argues that an explanation
that makes merely probable predictions can be tested only over against
its competitors. If O is an observation, and H 1 is a hypothesis, then we can
draw no conclusion from the mere fact that the likelihood of O given H is
low. To reject H 1 , Sober argues, we need an alternative, H 2 , which would
render the outcome more likely. We need to be able to show that
Pr(O|H 2 ) > Pr(O|H 1 ).
Why is this? It is, as Sober writes, because there is no probabilistic equivalent
of modus tollens. 29 There is no valid argument which runs:
(1) If H were true, O would be highly improbable.
(2) But O.
(3) Therefore H is not true.
It is easy to see why, for to adopt this line of argument would lead to unacceptable
consequences. If you win the national lottery, this is a highly
improbable outcome, given that the lottery was fair and that you bought
just one ticket. But it does not cast doubt on the hypothesis that the lottery
was fair. And if we have a line which is 1000 miles long, onto which we
drop a pin at random, the chance that it will fall just where it does is very
small. But that does not cast doubt on the hypothesis that it was dropped at
random. 30 It follows, Sober writes, that there is no “Law of Improbability
that begins with the premise that Pr(O|H) is very low and concludes that H
should be rejected.” 31
If Sober is correct, if probabilistic theories can only be tested comparatively,
it would seem that a solitary proposed theistic explanation can
receive short shrift. If there is no alternative against which to test it, then it
cannot be tested. And if it cannot be tested, it lacks one of the most important
desiderata of a satisfactory explanation. Sober illustrates this by referring
to Swinburne’s proposed theistic explanation of the existence of laws
of nature. Whatever else may be said about this argument, Sober writes,
it is not a scientifi c argument for the existence of God. Science is in
the business of testing alternative hypotheses against each other, where
these alternatives make different predictions. In the present example,