Despite protests to the contrary, intelligent design is a god of the gaps argument. Take a look at Discovery Institute blogs, and a large portion of the posts are essentially arguing that some aspect of biology or biochemistry is really, really complicated (for example, Howard Glicksman’s posts at Evolution News & Views). As if there are bunches of evolutionary biologists running around saying life is simple. So most intelligent design arguments boil down to “there’s no plausible evolutionary explanation for this aspect of biology, therefore it must have been designed.” And cdesign proponentsists insist on a high standard of evidence to consider an evolutionary explanation plausible. For example, here’s Michael Behe’s standard for believing that “…complex biochemical systems could arise by a random mutation and natural selection…”:

Not only would I need a step-by-step, mutation by mutation analysis, I would also want to see relevant information such as what is the population size of the organism in which these mutations are occurring, what is the selective value for the mutation, are there any detrimental effects of the mutation, and many other such questions. [Kitzmiller v. Dover, day 12]

On the origin of the blind cave fish Cryptotora thamicola, Anne Gauger says

What matters for intelligent design is that it has not been demonstrated that there is a stepwise selectable path from a fish ancestor to this, each step showing benefit and leading to this walking behavior and morphological change.

On the origin of Volvox, Dr. Gauger wants details (I’ve addressed some of her concerns previously):

Missing from this story, though, are the details necessary for this 12-step progression to occur. There’s the matter of incomplete cell division, cell separation later, and matrix formation. Then there’s the matter of specialization. To get the specialization of somatic from germ cells requires the development of at least three proteins…[skipping a big chunk here]

Where do all these new proteins come from? Either they come from cooption of old proteins, or by making new ones. I’ve already been over how hard those processes are to accomplish multiple times. Where does their regulation come from?

This is the sort of detail that requires answering if the white space in evolutionary thinking is to be filled.

On the origin of a Drosophila gene, Casey Luskin complains

In no case was there an analysis of how natural selection could have favored mutational changes that were shown to be likely along each step of an alleged evolutionary pathway; never was any detailed step-by-step mutational pathway even given.

So, obviously, intelligent design offers the detail evolutionary explanations lack: the mechanism(s) by which the designer twiddles DNA bases, the specific bases that have been twiddled, phenotypic effects of twiddlation, approximate dates of intervention…right? Strangely, Anne Gauger, who demands all the details for evolutionary explanations, doesn’t see that need for intelligent design explanations [emphasis in the following quotes added by me]:

ID is about design detection, and makes no statements about ongoing design or a design mechanism. We simply say that there are elements in the universe that give evidence of being designed. Anything further goes beyond what we can say. For example, we can say nothing about how (by what mechanism) design is instantiated.

Michael Denton also doesn’t see the need to identify a mechanism:

…the evidence for intelligent design is not undermined by conceding that the mechanism by which the design was executed is not understood. However, this does leave the question unanswered as to how the evolutionary process was directed, or to put it another way, how the designs manifest in the biological world were actualized.

Yes. Yes it does. Stephen Meyer explicitly rejects the idea that intelligent design should be required to explain the designer’s mechanisms:

There is a logical reason we cannot without further information determine the mechanism or means by which the intelligent agent responsible for life transmitted its design to matter. We can infer an intelligent cause from certain features of the physical world, because intelligence is known to be a necessary cause, the only known cause, of those features. That allows us to infer intelligence retrospectively as a cause by observing its distinctive effects. Nevertheless, we cannot establish a unique scenario describing how the intelligent agent responsible for life arranged or impressed its ideas on matter, because there are many different possible means by which an idea in the mind of an intelligent agent could be transmitted or instantiated in the physical world.

Just as there are many possible evolutionary routes by which a trait that evolved over millions of years might have come about. If we don’t know every detail of every change (“the population size of the organism in which these mutations are occurring, what is the selective value for the mutation, are there any detrimental effects of the mutation, and many other such questions…”), naturalistic explanations are implausible. For evolution, anything short of a “step-by-step, mutation by mutation” reconstruction is a fatal flaw; for intelligent design, the lack of any proposed mechanism at all is just a logical necessity.

[EDIT: spelling]