The claim that ID is not a scientific theory implies that even if there were
scientific evidence against evolutionary theory, which was originally
introduced as an alternative to design, that would not constitute any
scientific evidence for ID. We might have to give up evolutionary theory,
but then we would be constrained by the canons or definition of science
to look for a different scientific, i.e., nonpurposive, explanation of the
development of life, because science prohibits us from even considering
ID as a possible alternative explanation, one whose eligibility would
otherwise be enhanced by the rejection of the leading scientific expla-
nation, namely evolutionary theory.
What would it take to justify the claim that there are propositions
such that the discovery of evidence against them can qualify as science,
but evidence in favor of them cannot? Someone who accepts this view
would probably extend it to propositions about ghosts or extrasensory
perception. Research showing that effects that some benighted souls
have attributed to ghosts or mental telepathy can be explained in a
perfectly naturalistic way would count as science, but any argument
that the evidence does not support those explanations, and that
significant experimental or observational data are better explained
by ghosts or by ESP, would not count as science, and could therefore
be ruled out of consideration. On this view it would not even be a
false scientific claim.
The idea is that any naturalistic or nonspiritual explanation of a phe-
nomenon can be either confirmed or disconfirmed by empirical evi-
dence together with causal and probabilistic reasoning. No empirical
evidence against such a nonspiritual alternative, however, nor any
other kind of empirical evidence, could provide a reason for believing
the spiritual hypothesis. Belief in something like that is necessarily the
result of a different cognitive process, having nothing to do with the
scientific evaluation of empirical evidence (rank superstition or blind
faith, to give it its true name). I submit that this way of drawing the
boundaries around science depends not on a definition but on the
unspoken assumption that all such propositions are obviously false—
there are no ghosts, there is no ESP, and there is no god—so that to
invoke such things to explain any observed phenomenon, even one for
which no other explanation is available, reveals a disposition to take
seriously a possibility that a rational person would not consider. Without
this assumption the exclusion of ID from consideration cannot be defended.