The supposed argument from ignorance....

...also known as the god-of-the-gaps. I.e., science will fill in the gaping holes it has on the issue of origins, if we just wait for it. Typically, this argument is followed up by some emotional conditioning with respect to religion and science, implying that we should keep waiting for science, keep faith in it. It is used very often on the American Left, because they want to have faith in science while simultaneously pretending that they and science are opposed to religion based on facts.

An answer,
".....Australian philosopher Alan Olding, in commenting on thepersistent use of the argument from-ignorance or god-of-the-gaps objection against the work of Michael Denton and Michael Behe, writes, The phrase 'god of the gaps' is nothing more than a question-begging insult meant to stop the flow of argument before it has barely started.
(See his article: Maker of Heaven and Microbiology, Quadrant, January-February 2000.)

To see that the argument-from-ignorance objection is not a magic wand for silencing intelligent design, let's begin with a reality check. When the argument-from-ignorance objection is raised against intelligent design, who exactly is accused of being ignorant? It's natural to think that the ignorance here is on the part of design theorists, who want to attribute intelligent agency to biological systems. If only those poor design theorists understood biology better, those systems would readily submit to mechanistic explanation. Thus, when I lecture on university campuses about intelligent design, a biologist in the audience will often get up during the question-and-answer time to inform me that just because I don't know how complex biological systems might have formed by the Darwinian mechanism doesn't mean it didn't happen that way. I then point out that the problem isn't that I personally don't know how such systems might have formed but that the biologist who raised the objection doesn't know how such systems might have formed and that despite having a fabulous education in biology, a well-funded research laboratory, decades to put it all to use, security and prestige in the form of a tenured academic appointment, and the full backing of the biological community, which has also been desperately but unsuccessfully trying to discover how such systems are formed for more than one hundred years. Who is ignorant here? Not just the design theorists, but the scientific community as a whole. In fact, it's safe to say that the biological community is clueless about the emergence of biological complexity. How so? Because the material mechanisms to which the biological community looks to explain biological complexity provide no cluefor how those systems might realistically have come about. The problem, therefore, is not ignorance or personal incredulity but global disciplinary failure (the discipline here being biology) and gross theoretical inadequacy (the theory here being Darwin's).

Now, such vast ignorance is not something one typically wants to advertise. A few biologists, however, have now come clean. These include James Shapiro and Franklin Harold, neither of whom supports intelligent design. In a review of Michael Behe's book Darwin's Black Box (National Review, September 16, 1996), James Shapiro, a molecular biologist at the University of Chicago, conceded that

there are no detailed Darwinian accounts for the evolution of any fundamental biochemical or cellular system, only a variety of wishful speculations. It is remarkable that Darwinism is accepted as a satisfactory explanation for such a vast subject--evolution--with so little rigorous examination of how well its basic theses work in illuminating specific instances of biological adaptation or diversity.

Five years later, cell biologist Franklin Harold wrote a book for Oxford University Press titled The Way of the Cell. In virtually identical language, he noted, "There are presently no detailed Darwinian accounts of the evolution of any biochemical or cellular system, only a variety of wishful speculations."

David Ray Griffin, also no supporter of intelligent design, is a philosopher of religion with an interest in biological origins. Commenting on the evolutionary literature that purports to explain how evolutionary transitions lead to increased biological complexity, he writes (in his book Religion and Scientific Naturalism),

There are, I am assured, evolutionists who have described how the transitions in question could have occurred. When I ask in which books I can find these discussions, however, I either get no answer or else some titles that, upon examination, do not in fact contain the promised accounts. That such accounts exist seems to be something that is widely known, but I have yet to encounter someone who knows where they exist.

At a recent debate with Brown University biologist Kenneth Miller, I quoted Franklin Harold on the absence of detailed Darwinian accounts for the evolution of complex biological systems. Miller did not challenge Harold's claim. Instead, he impugned Harold's credibility by remarking that Harold was old, having retired fifteen years ago."
(The Design Revolution
By William Dembski :213-215)

The Left is opposed to religion, science is not.