Theism and Explanation - Appeared-to-Blogly

Inference to the Best Explanation 107
background: the relevant evidence is everything (except God himself). I
think this argument is fl awed, for reasons to which I shall return (7.2.2). In
any case, having dismissed background knowledge, Swinburne is left with
simplicity and scope. He argues that of these two the criterion of simplicity
is the more important, and that on this criterion theism ranks very highly.
Given this conclusion regarding prior probability, there remains the task
of assessing the degree to which the evidence supports theism. Swinburne
does this by performing the requisite Bayesian calculations. He admits that
his probability estimates are “arbitrary,” but claims that they do “capture,
within the roughest of ranges, the kinds of probabilities involved.” 28 At
fi rst, Swinburne leaves aside the evidence of religious experience, the force
of which depends upon whether a person has herself had a religious experience,
29 and the evidence of history, which he considers at more length elsewhere.
Leaving these aside, Swinburne concludes that “it is something like
as probable as not that theism is true.” 30 In other words, the posterior probability
of theism is roughly 0.5. But he argues that if we add the evidence
of religious experience and of history, then we can conclude that “theism is
more probable than not.” 31
6.1.3 Abductive Reasoning
Even if one grants the force of these calculations—and each step along the
path is contestable—one might argue that they do not take us very far. The
Christian theist will still want to demonstrate that his particular variety of
theism, with all its additional claims, is probably true. And this is no easy
task. Alvin Plantinga, for instance, argues that even if we assign a probability
of 0.9 to theism, we will not be able to demonstrate the probable truth
of the Christian faith. Making generous estimates along the way, Plantinga
calculates that the probability that Christianity is true could not exceed
0.35. 32 But let me leave such considerations aside, for my primary interest
here is in the structure of Swinburne’s arguments and the criteria he is
using. What can we say about the structure of these arguments?
My proposal is that Swinburne’s overall argument is best thought of as
a type of abductive reasoning, although he himself does not employ this
term. In arguing that what we observe around us is “such as we have reason
to expect if there is a God, and less reason to expect otherwise,” 33 Swinburne
is in fact arguing not inductively but abductively.
It is true that abductive reasoning could be supported by an inductive
argument. One could set out an inductive argument—one that argues from
past instances—in support of the second premise of Peirce’s abductive
schema (2.1.2). If all observed events of type E were produced in the manner
indicated by hypothesis H, this would give us some reason to think that
H was the explanation of E. Intelligent design advocate Stephen Meyer, for
instance, to whose work I referred earlier (2.1.1), offers an argument of precisely
this form. In what has become a controversial article, 34 Meyer offers