212 J.J.C. Smart
to do my best for the theist. The counter-argument would rest largely on
the anthropocentricity (or perhaps biocentricity) of the notion of purpose,
especially as it is elucidated in evolutionary theory as a result of chance and
natural selection. Even theists are prone to stress the inscrutability of the
nature of God, and especially because of the existence of evil, to wonder
about whether God would have purposes in any human sense of the world.
At the best our wonder and awe at the existence and beauty of the universe
might suggest a form of pantheism more related to F.H. Bradley’s Absolute
or Sankara’s Brahman. (If these notions make sense.)
7 The Fine-Tuning Argument: Bayesian Considerations
Bayes’ theorem in the theory of probability is concerned with the probability
of a hypothesis h given evidence e. It says that
Prob(h/e) = [Prob(e/h)×Prob(h)]/ Prob(e)Thus it helps that eshould follow from or be made highly probable by h. It
also helps that hitself should be antecedently probable. Most importantly for
hgiveneto be high it is important that the antecedent probability of e should
be low. The proponent of the fine-tuning argument puts the antecedent
probability of eto be very low. The lower e, the higher observation of eraises
the probability of h. So the proponent of the fine-tuning argument lays stress
on the fact that the fine tuning is antecedently highly improbable, i.e. that it
is surprising. If h is the theistic hypothesis, the argument persuades us that
the fine tuning e, though antecedently improbable, is quite to be expected
if God exists and has created a universe susceptible to the emergence of life
and consciousness (and, for that matter, such things as stars and galaxies).
However, Prob(h) occurs in the numerator of the right-hand side of the equa-
tion above. If Prob(h) is very very small it may keep Prob(h/e) small despite
Prob(e) being very small: for example, some people might put the existence of
evil as greatly reducing the probability of the theistic hypothesis.
Still, how small Prob(h) could be depends on the nature of the theistic
hypothesish. Thus someone might give a very low value to the antecedent
probability of the existence of John Leslie’s God as an ethical principle that
brings value into existence, perhaps because he or she gives a high probability
to non-cognitivism in meta-ethics. Can an ‘is’ somehow be explained by an
‘ought’? (However, in the next section I shall give a half-hearted – or maybe
quarter-hearted – defence of a somewhat Leslie-like position.)
Someone who was convinced of the non-existence of God because of the
existence of evil would put Prob(h) as zero or perhaps infinitesimal. Those of