As a historian speaking on various aspects of my work on Alfred Russel Wallace (i.e. Alfred Russel Wallace’s Theory of Intelligent Evolution and Alfred Russel Wallace: A Rediscovered Life), I have often juxtaposed his contributions with Darwin. I point out that young Charles’s evolutionary ideas were influenced by his early associations with the radical group of freethinkers with whom he came in contact as a teenager for nearly five months between 1826 and 1827 in Edinburgh. This group, the Plinian Society, and his early mentor and confidant, Robert Edmond Grant (himself an unapologetic materialist), formed the seminal intellectual backdrop for the construction of Darwin’s evolutionary theory long before he ever stepped foot on the HMS Beagle. These antecedents to Darwin’s development as an evolutionist have prompted me to conclude that the "ism" that bears his name, Darwinism, "is essentially a metaphysic of naturalistic materialism resting upon a series of biological speculations."
In discussions with Darwin defenders, a recurrent criticism I receive is that this is just the genetic fallacy. The genetic fallacy is the assessment of an argument or theory based upon its origin, history, or source rather than the argument or theory itself. It is a specific instance of the broader category of fallacies of relevance. Now a moment’s reflection will bring to mind numerous exceptions and caveats to the genetic fallacy. Otherwise, all historical inquiry would be ruled out of bounds and Clio subjected to a logician’s gag order. Indeed, as Kevin Klement has pointed out, not all forms of genetic reasoning are false. Writes Klement,
It bothers us when someone is able to identify the cause of one of our beliefs as being something other than the grasp of its truth or likely truth, even those of us (and perhaps especially those of us) with significant logical training. The textbook account of the genetic fallacy would make this a mystery.
With this as context, permit me to explain why the argument I outline above does not succumb to the genetic fallacy. To make this charge stick it would need to be shown that the historical processes in developing Darwin’s evolutionary ideas are irrelevant to the theory itself. However, Darwin himself tied the strength of his theory to those processes. In his autobiography he insists, "I worked on true Baconian principles, and without any theory collected facts on a wholesale scale . . . ." Elsewhere Darwin claimed to have come by his theory solely "by patiently accumulating and reflecting on all sorts of facts" and only after five years of this fact-gathering did "I allow myself to speculate on the subject." Darwin went to great lengths to sketch out a process of discovery in which alleged "fact-finding" preceded all theorizing. His purpose in doing this seems obvious: he felt the need to separate his evolutionary theory from any a priori assumptions. In short, Darwin himself regarded the methodological process of his discovery as an important foundation upon which his theory was built. Darwin clearly wanted his theory to be seen as wholly evidentiary, and for a theory premised upon the primacy of methodological naturalism this was of understandable importance.
But is Darwin’s account accurate? An examination of the actual historical sequence of events shows it, in fact, to be either self-delusional or disingenuous. Gertrude Himmelfarb points out in Darwin and the Darwinian Revolution that Darwin’s notebooks from 1836 to 1839 and later show that "he was speculating boldly from the very beginning." Howard Gruber’s Darwin on Man asserts that "his actual way of working . . . would never have passed muster in a methodological court of inquiry among Darwin’s scientific contemporaries." Far from dismissing the historical processes of the theory’s development, Gruber emphasizes that misunderstandings
arise from Darwin’s desire to defend his unpopular views by suggesting that he had been driven to them by a mass of unassailable evidence, rather than the less acceptable reality that much of his evidence had been patiently assembled, but only after his views were quite well developed.
Why "less acceptable"? Because Gruber — and indeed Darwin himself — understood that speculation prior to evidence might well invite the charge that the alleged "facts" were merely arranged to fit the theory rather than the other way around, a cutting of the toes to fit the shoe as it were. The arguments I have made demonstrate that Darwin was introduced to the metaphysics of materialism and methodological naturalism long before he gathered any evidence about evolution. That the theory he ultimately constructed looked much like the ideas he heard advanced by the Plinians and Robert Edmond Grant strongly suggests that Darwin’s theory is, in fact, a metaphysic wrapped in a veneer of scientific explanation. In speaking of Darwin’s book The Expression of the Emotions in Man and Animals (1872), even sympathetic biographers like Adrian Desmond and James Moore admit, in their book Darwin, that "like the Plinian phrenologists in particular, forty-five years before at Edinburgh, he made Sir Charles Bell’s pious Anatomy and Physiology of Expression his prime target." These early metaphysical exposures were not transitory excursions into a youthful materialism, they were foundational to Darwin’s work as a mature naturalist.
Cornelius G. Hunter’s book Darwin’s God astutely observes that Darwinian evolution "is one of the great examples of humanity’s quest for objective knowledge. It proposes to explain the world without presupposing anything about the world." But alas this radical "blind presuppositionalism" is unattainable. "To understand evolution one must understand its metaphysical influences, but ever since Darwin," writes Hunter, "evolution has been advertised as an objective conclusion — a neutral path to knowledge. According to its adherents, the theory of evolution is not beholden to any religious or otherwise metaphysical assumptions." Hunter demonstrates that this claim is simply disingenuous.
In the final analysis, then, the charge of genetic fallacy fails since my argument that Darwin’s early exposure to materialist ideas and their interesting resurrection throughout his notebooks (e.g., his approving references to Hume and Comte, his comment that thought is a mere "secretion" of the brain, and similar musings) bears a direct relationship to the theory as expounded in the Origin and Descent of Man. The problem isn’t common descent or even natural selection per se (though their verifications are open to scrutiny on quite independent grounds) but rather the extent and depth of their explanatory power, and these are philosophical as much as evidentiary questions. Alfred Russel Wallace, in fact, examined the same evidence as Darwin but came up with intelligent evolution instead of Darwin’s reductionist formulation. The notion that the timing and nature of Darwin’s own metaphysic is completely irrelevant to the theory he constructed is simply untenable. The metaphysic, in fact, was intrinsic to Darwin’s theory from the beginning. Historians have long asked, when did Darwin become an evolutionist? But a more revealing question is, when did Darwin become a materialist? The answer reveals much about his theory and its a priori commitments.