Editor’s note: This article is excerpted from Taking Leave of Darwin: A Longtime Agnostic Discovers the Case for Design, by Neil Thomas, newly released by Discovery Institute Press.

When Darwin makes the attempt to explain the crucial point of The Descent of Man, humankind’s supposed descent from ape-like ancestors, he speculates somewhat vaguely on the question of whence we as a species got our superior brains: “The mental powers of some earlier progenitor of man must have been more highly developed than in any existing ape, before even the most imperfect form of speech could have come into use; but we may confidently believe that the continued use and advancement of this power would have reacted on the mind itself, by enabling and encouraging it to carry on long trains of thought.”¹

A Just-So Story

The passage has the disconcerting tone of a just-so story. How, one might legitimately ask, did one ape “happen” to get its superior cognitive capacities? What was the vera causa of its braininess? And how did this cognitive superiority trigger correlated changes in the brain? In the light of present-day scientific advances, these seem like shallow assertions, inadequate to account for what we know about those labyrinthine co-adaptive changes necessary for the process he describes to function effectively.

On another point, this passage and many others like it would be a gift to linguistic specialists in discourse analysis or to those whose specialty is in the deconstruction of advertising propaganda. Darwin’s reiteration here and elsewhere of the phrase “we may confidently believe” veils the tenuous truth-value of what he proposes, which is finally little better than a guess. This mode of assertion is uncomfortably reminiscent of the wearisomely repeated phrase of the ex-PR-man turned Prime Minister of Great Britain, David Cameron: “Let us be clear” — which you just knew was going to be the rhetorical prelude to his making a partisan point vulnerable to all those objections he was trying to head off.

Nothing New for Darwin

Such rhetorical legerdemain was nothing new for Darwin. He had recourse to it more than a few times in the Origin. We find it in evidence, for example, where he seeks to persuade us that the eye was not designed but somehow fell into place as the result of a myriad of chance selections over time:

That many and serious objections may be advanced against the theory of descent with modification, I do not deny. I have endeavoured to give them their full force. Nothing at first can appear more difficult to believe than that the more complex organs and instincts should have been perfected, not by means superior to, though analogous with, human reason, but by the accumulation of innumerable slight variations, each good for the individual possessor. Nevertheless, this difficulty, though appearing to our imagination insuperably great, cannot be considered real if we admit the following propositions, namely, — that gradations in the perfection of any organ or instinct which we may consider, either do now exist or could have existed, each good of its kind, — that all organs are, in ever so slight degree, variable, — and, lastly, that there is a struggle for existence leading to the preservation of each profitable deviation of structure or instinct. The truth of these propositions cannot, I think, be disputed.²

What has Darwin said there? According to my reading he suggests that, even though you or I might find unbelievable the idea of almost unimaginably complex structures like the eye coming about by slight and undirected variations over time, the difficulty lies all in our imagination. He then points to three quite doubtful propositions as if they were self-evidently true and as a (hoped for) confirmation of his point, all in the hope that we will come round to his way of thinking. But asserting that a firmly felt instinctive reaction is mere imagination is only that, an assertion, not a demonstration; and labeling disputable points indisputable no more makes them so than praising the proverbial “emperor’s new clothes” cures his nakedness.

Notes

1. Darwin, The Descent of Man, 110.
2. Darwin, On the Origin of Species, 337.