This type of argument almost always represents a logical fallacy,
in fact, it even has a name: the argument from the false (or
missing) alternative.
The argument works only for the very special case, almost never
encountered in the real world, where there are only two mutually
exclusive possibilities. In the present case there are actually
multitudinously many possibilities since one cannot really
test either "evolution" or "creation" but rather specific models
about how these may have occurred. There are many many
possibilitites of each, for evolution we have say N models
E1, E2, E3, ..., EN and for creation we have say M models
C1, C2, C3, ..., CM. In practice its often worse than this
since we would usually not test E5, say, all at once but
rather some sub-theory of E5. So each Ei might be further
divided into Ei1, Ei2, ...
So, the idea is that evidence against model E7, say, provides
no evidence *for* C2. It is only evidence against E7.
Further, evolution and creation are not necessarily mutually
exclusive. As witness to this, there are many here who like
to refer to themselves as Evolutionary Creationists. So we
have another set of models EC1, EC2, EC3, ...
Further, there is another potentially large set of models
that no one has thought of yet: NOTOY1, NOTOY2, NOTOY3, ...
In my own experience, I have most often seen this argument
presented by Creationists. For example, a response by
Gillian Brown regarding the Dawkins interview was posted
on the asa list. The next to last paragraph went as
follows:
========================
"Behind the smokscreen thrown up by your cry of "lies, lies" is a very
important question: What is the origin of new information? We do
know that great variation within species results from rearrangement or
loss of genetic information, but this does not explain
macroevolutionary transition from simple life forms to complex ones
with far greater genetic information. Clearly, if new functional
information cannot be shown to come through evolutionary mechanisms,
then the only alternative is intelligent design." -- Gillian Brown
=========================
Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University
"It appears to me that this author is asking
much less than what you are refusing to answer"
-- Galileo (as Simplicio in _The Dialogue_)