I am grateful for the opportunity to clarify and expand upon my earlier argument occasioned by the excellent responses offered by Stephen Barr and Kenneth Kemp in the past two days. The primary critique of my “eye test” argument advanced by both of my critics rests upon a simple misunderstanding of my meaning; this simple misunderstanding implies, however, a related misunderstanding both of Darwin’s thought itself and of the implications of evolutionary theory more broadly.

The clearest way of showing these related misunderstandings lies in attending to the title of Darwin’s great work: “The Origin of Species.” This title has a double meaning, both of which Darwin clearly intends in an intimately connected way.

First, Darwin obviously means to answer the question of how the living things we see around us got to be here in the first place. With respect to this meaning, Darwin intends to combat the previously dominant idea “that species were immutable productions, and had been separately created.”

In his introductory “Historical Sketch,” Darwin singles out the primary foil for his theory to which he frequently recurs throughout the Origin: the idea that a Creator originally and separately made each of the types of living being we see around us. Regardless of whether there is actually any contradiction between Darwinian evolutionary theory and biblical religion, Darwin quite explicitly understands his Origin to be a competitor with a literal interpretation of the Book of Genesis. It is no mere coincidence that Darwin himself, as well as his most energetic early defenders and allies such as T.H. Huxley and Herbert Spencer, was agnostic.

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Barr and Kemp are entirely correct in their insistence that current mainstream understandings see no conflict between evolution and religion (partly the result of admirable work that Barr and Kemp have each done themselves), but this rapprochement is a relatively recent development—“traditionally” this perceived conflict has been of paramount importance. If we understand evolution, religion, and their relation better today than did Darwin himself or Huxley and Wilberforce in their famous debate, then so much the better for us—though I must admit I am more hesitant than most to pronounce definitively upon this point.

The second, much less obvious meaning of Darwin’s title is evident from the concluding paragraph of his discussion of “Doubtful Species”: “From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other.” In other words, the “origin of species” is also arbitrary human convention as opposed to something within or concerning living beings themselves. A philosopher might call Darwin a “nominalist”: Names like “squirrel,” “elephant” or “human being” don’t refer to anything with a reality beyond our own minds.

Darwin tightly weaves the two meanings of his title together in the following way: “The term species thus comes to be a mere useless abstraction, implying and assuming a separate act of creation.” If one thinks that God created types of living beings separately, one will be inclined to think that “species” refers to something real rather than constructed by us for the sake of convenience.

Similarly, the opinion that there is some reality to the idea of “species” fits comfortably with a belief in separate creation. Darwin clearly takes his evolutionary theory to simultaneously and relatedly combat both a belief in separate creation by God and a belief in the reality of the idea of species.

The first meaning of Darwin’s title—that relating to religion—has been thoughtfully and impressively explored by Archbishop Zycinski (translated by Kemp) and Barr himself. It is the second meaning—that relating to the reality of species—to which my “eye test” argument is primarily directed. Both Barr and Kemp take my account of sense experience in a far more literal, limited, and simplistic sense than I had intended. Barr notes that as human beings our sense experience is always accompanied by some sort of interpretation, or processed rationally in some way. Kemp similarly asserts that our senses only take us so far before reason has to take over. With these statements I am in complete agreement.

Where I part ways with Barr and Kemp is in insisting on the validity of the more basic form of reasoning associated with Barr’s and Kemp’s poor hapless “layman.” In a modern society enamored of ever-increasing specialization, particularly in the areas of science and technology, most of us tend to assume that the only way to really know something is to get a Ph.D. in it.

Yet even if you have a Ph.D. in one subject, you are most likely doomed to remain an ignorant layman with respect to all the others. Knowledge has become increasingly stilted and compartmentalized since the early modern era. This conception of knowledge, however, misrepresents the fundamental intelligibility of a common and interconnected world of experience within which all of us—rocket scientists and laymen alike—live.

The sort of “eye test” I have in mind, and which I believe poses an underappreciated challenge to Darwinian evolutionary theory, involves much more than simply “looking” or physically seeing; it is, rather, precisely what Aristotle describes as “the originative source of scientific knowledge” in his Posterior Analytics. According to Aristotle, all scientific knowledge must build upon previous knowledge, leading to the problem of knowledge’s ultimate origin. This origin lies, according to Aristotle, in a process of induction or intuition whereby sense impressions become memories, and memories become “experience.”

This experience is defined by abstraction—we human beings experience the world in terms of stable and defined universal concepts, and these concepts in turn form the building blocks of all subsequent knowledge. Our experience in this special Aristotelian sense, for example, tells us that elephants are different in kind from human beings, and not in degree, however large this degree may be. Our experience, on its own and apart from whatever scientific education we may possess, tells us that human beings are separated from elephants by rationality—not by millions of years of differential development.

It is precisely this process of Aristotelian intuition—a process that allows equal access on the part of layman and specialist alike to a common world of experience—that constitutes a sort of “eye test” in serious tension with evolutionary theory. The very way in which we human beings know the world around us—not certain troublesome facts or particular ideas and beliefs, but our very intellectual constitution—is inextricably bound up with the stability and distinctness of the types of things, or “species,” we observe.

Evolutionary theory, as Darwin explicitly emphasized, carries with it a decisive rejection of the truth of this stability and distinctness of species or types of things. The problem isn’t “seeing more” versus seeing less, or the perspective of millions of years versus thousands—it is that evolutionary theory, as Darwin saw exceedingly clearly, appears to require a repudiation of our fundamental intellectual affinity with the world around us, an affinity in virtue of which, one might add, we have been said to be created “in the image and likeness of God.”

But what of the question raised by Kemp regarding feasible alternatives to the evolutionary account? Kemp wonders how one can explain the “morphological and genetic similarity” among rodents without recourse to evolutionary theory, just as Darwin wondered in the Origin how one could explain the ordered arrangement of living beings in “groups under groups” without his account of modification and descent. While sketching a plausible alternative in a satisfactory manner would be a complex undertaking, for the moment I would simply pose a question to Darwin and Kemp: Wouldn’t we expect to see the same morphologically and genetically overlapping and hierarchically organized organic world that scientists have uncovered if we appealed to the theory of a separately-creating Creator who has an intelligence analogous to our own? And if we would, then why would such a theory be objectionable to pious scientists like Barr?