Darwinians have long scoffed at the notion that there are limits to the miracles that natural selection and genetic mutation can perform. They're fond of taking evidence of relatively small variations in the genotypes and phenotypes of a population of organisms - what's called microevolution - and then extrapolating from those tiny changes to the enormous diversity of living things we see in our world. In other words, the argument goes, if one bacterium can develop a resistance to a certain antibiotic, then given enough time bacteria can develop into elephants, or something like that.
It is the argument of Michael Behe's The Edge of Evolution that this extrapolation is not grounded in empirical evidence and is, in fact, an assumption based upon materialist metaphysics. If natural processes are all there are, the reasoning is, then the extrapolation just has to be licit, and the diversity of life simply must have arisen by slow gradual changes over long periods of time.
Behe's counter-argument is technical and empirical, but there's an earlier case made against this kind of extrapolation which is much less technical, just as persuasive, and pretty humorous besides. I don't know if the author had Darwinism in mind when he wrote it but what he says about the hazards of extrapolation certainly applies to the Darwinian view of life:
In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. This is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolithic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing rod. And by the same token, any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. -----Mark Twain
Darwinians begin with the fact that things change and deduce from that humble observation that the entire cosmos is a result of purely physical, mechanical processes. Like Twain says, one gets such wholesale returns of conjecture out of such a trifling investment of fact. Perhaps that's part of the appeal of Darwinism.
RLC