If the correct explanation for a phenomenon happens to be supernatural,
the naturalistic method of science will miss it. "With creationist
explanations disqualified at the outset, it follows that the evidence will
always support the naturalistic alternative."
Nobody has ever come up with a useful definition of supernatural. By
most definitions, something having an effect on nature makes that
something a part of nature itself. So any explanation for something we
see in nature can be considered natural by definition.
We cannot observe the supernatural, so the only way we could reach the
supernatural explanation would be to eliminate all natural
explanations. But we can never know that we have eliminated all
possibilities. Even if a supernatural explanation is correct, we can
never reach it.
Suppose we do conclude that a supernatural explanation is correct. It
is impossible, even in principle, to distinguish one supernatural
explanation from another. Many people, including many scientists, are
willing to accept certain supernatural explanations on faith. There is
nothing wrong with that as long as they do not claim special privilege
for their faith. Some people, however, are not satisfied unless others
believe as they do; this group includes all those who want to make the
supernatural a part of science. Since they cannot make their case by
using naturalistic evidence, they must resort to other means, such as
force of arms. (This is not hyperbole. Such groups continually
attempt to get political enforcement on their side.)
If we do miss a supernatural explanation, so what? Supernatural
explanations cannot be generalized, so the explanation does not matter
anywhere else. The usefulness of science comes from the ability to
apply findings to different areas. Any supernatural explanation would
be useless.
Explanations in terms of the supernatural are evaluated to the extent
it is actually possible to do so. For example, scientists have
investigated faith healing (Benson et al. 2006) and creationist claims
about a global flood and age of the earth.
Creationist accounts of origins are not disqualified. People are
free to believe whatever religion they choose. P. E. Johnson and
others like him merely object to their religion not being taught as
science to the exclusion of all other religious interpretations (not to
mention to the exclusion of all of science).
References:
Benson, H. et al. 2006. Study of the Therapeutic Effects of
Intercessory Prayer (STEP) in cardiac bypass patients: a multicenter
randomized trial of uncertainty and certainty of receiving intercessory
prayer. American Heart Journal 151(4): 934-942.