Jeff Epler
One common argument for theism is based on the observation that the universe is finely tuned to produce life, and that this is an incredibly unlikely event. This seems to be the position to which theists have retreated since the claim that the origin of life from non-life has been shown to be absurd. Unfortunately, the mathematics of probability and statistics do not support the claim that a finely tuned universe gives evidence for God.
Divide all the possible universes into two sets, those highly suited to biological proceses and those less than highly suited to biological processes. Leaving aside considerations of physics which would be likely to give rise to biological processes very different from those which exist now on earth, it is a reasonable clain that ``only those universes suitable to life will come to contain life,'' or at least ``only a very few universes unsuitable to life will come to contain life.''
Now, consider all the universes in which a creature would pose a theory about a deliberate fine-tuning of the universe and wish to test that theory. Most of those creatures will in fact be in a universe which is fine-tuned, and very few (or even no) creatures will be in a universe which is not tuned for its type of biology. So no matter the probability of a fine-tuned universe, the probability that a universe with a creature will be fine-tuned is very close to a certainty.
Speaking mathematically, let "A" be the probability that the universe is
fine-tuned for the kind of life which exists on earth, and "B" be the
probability that earthlike life exists in a universe. Then "the probability
of A given B" is
but 
, so
but our premise is that 
, the probability of a universe
which is not finely tuned for life but contains life, is 0 or very close to
0. thus,
Mathematics backs up intuition: In universes with life, the universe is extremely likely to be finely tuned to produce life. Thus, exactly as the improbability of life produces no evidence for theism, the fact that the universe is finely tuned to produce life is also not evidence for theism.