Recently, one of my philosophy colleagues, upon learning of my interest in intelligent design, asked me what I thought about the criticisms leveled at design thinking by 18th-century Scottish philosopher David Hume. According to my colleague, many think Hume destroyed once and for all the intellectual coherence of design theories. Therefore, he assumed I would have an opinion on the matter. I am not trained as a philosopher, and I had to confess that I had little knowledge regarding Hume’s arguments against design. But this question sent me scurrying to the library for some unplanned research. And I’m glad for this, for after engaging with Hume’s work, I came to the unexpected and somewhat ironic conclusion that while Hume’s arguments might have had some currency in their 18th-century context, the findings of modern science have actually rendered them much less convincing.

Hume’s anti-design arguments are found in his Dialogues Concerning Natural Religion. Here, he uses the character Cleanthes as the spokesperson for design, with Philo being the one to convey Hume’s own critical thoughts. A major part of Hume’s critique revolves around what he sees as the great dissimilarity between the world of nature and the world of human artifice. All knowledge, he says, comes through experience and we experience humans designing things all the time. But nature is unique and completely unlike the world of human contrivance, leaving us devoid of experience to draw on. We can thus draw no analogy between the work of human designers (of which we have much experience) and a designer of nature (which is singular and unlike anything produced by humans). 

The Argument for Design

In one passage, Hume has Cleanthes clearly state the argument from design:

Look around the world: Contemplate the whole and every part of it: You will find it to be nothing but one great machine, subdivided into an infinite number of lesser machines….The curious adapting of means to ends, throughout all nature, resembles exactly, though it much exceeds, the production of human contrivance….Since therefore the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of nature is somewhat similar to the mind of man; though possessed of much larger faculties, proportioned to the grandeur of the work which he has executed.

But Hume does not buy Cleanthes’s analogy:

If experience and observation and analogy be, indeed, the only guides which we can reasonably follow in inferences of this nature; both the effect and cause must bear a similarity and resemblance to other effects and causes, which we know, and which we have found, in many instances, to be conjoined with each other.

Since nature, in Hume’s view, is unique and unlike anything we can ascribe to human contrivance, we have no experience of nature being designed and cannot analogize it to human artifice, of which we have much experience. 

What the Future Held

Little could Hume know what the future would hold — the discovery that at the cellular level, all organisms are driven by molecular machinery that looks and acts uncannily like the machines produced by humans, but far more sophisticated. Whether it be the bacterial flagellum with its rotor, stator, clamps, and bushings, the efficient whirring of the ATP synthase, or the mechanical movements of the kinesin walking protein (see below), every cell is a vast factory of biochemical processes and information processing being carried out by a nano-technology of unbelievable complexity and sophistication, but a technology nonetheless. Hume’s argument for the dissimilarity between natural and human-designed entities begins to melt away. If living organisms are indeed built on a nano-technology that mimics human-designed technology, and if similar effects do have similar causes, then molecular machines must be intelligently designed just like human machines. Cleanthes’s analogy seems to hold in a way that Hume could never have foreseen.

William Paley may be hinting at Hume’s critique in the following passage from Natural Theology:

I have sometimes wondered why we are not struck with mechanism in animal bodies as readily and as strongly as we are struck with it, at first sight, in a watch or a mill. One reason of the difference may be, that animal bodies are, in a great measure, made up of soft flabby substances, such as muscles and membranes; whereas we have been accustomed to trace mechanism in sharp lines, in the configuration of hard materials, in the moulding, chiselling, and filling into shapes of such articles as metal or wood. There is something, therefore, of habit in the case; but it is sufficiently evident that there can be no proper reason for any distinction of the sort. Mechanism may be displayed in the one kind of substance as well as in the other.

Hume wanted to maintain the distinction between nature and human artifice as the heart of his argument against design. But modern science sides with Paley. Below the level of flabby muscles and membranes, organisms do indeed display the sharp lines of mechanism. 

Mind and Matter

In a second criticism of Cleanthes, Hume has Philo say to his friend:

Let us once more put the argument from design to trial. In all instances which we have ever seen, ideas are copied from real objects, and are ectypal, not archetypal….You reverse this order, and give thought the precedence. In all instances which we have ever seen, thought has no influence upon matter, except where that matter is so conjoined with it, as to have an equal reciprocal influence upon it.

In other words, minds can only influence matter making up the body to which the mind is attached. Here again, modern science undermines Hume’s point. We now know about quantum theory and the collapsing of the wave function of an elementary particle when it is observed and measured. Minds profoundly influence matter at the most fundamental level, not to mention research showing the possible influence of mind on random number generators or even in intercessory prayer. And certainly, the world of human culture and technology powerfully testifies to the power of mind to force matter into configurations that would never occur if left to natural laws (as I type this on a plastic keyboard). Hume’s criticism falls flat. Minds have transformed the world of matter. 

In a somewhat humorous tip of the cap to irreducible complexity, Paley noted how a structure like the epiglottis could not have evolved gradually from a simpler form, because with only half an epiglottis, we would all choke to death! Paley comes off to me as a far keener observer of nature than Hume. And now from the vantage point of 21st-century science, we can see even more clearly the bankruptcy of Hume’s skepticism. There is no sense in which we can say that Hume destroyed the intellectual coherence of design thinking. Paley could already see this in 1802. How much more clearly can we see it today in the light of modern scientific advancement?