it actually to answer; who comprehended its construction, and designed its use.’ If a watch implies a watchmaker, then how could the exquisite purposefulness of an animal not imply an animal-maker? ‘Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater or more, and that in a degree which exceeds all computation.’
Paley’s argument from design was not new. It was Newton’s logic applied to biology. Indeed, it was a version of one of the five arguments for the existence of God advanced by Thomas Aquinas six hundred years before: ‘Whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence.’ And in 1690 the high priest of common sense himself, John Locke, had effectively restated the same idea as if it were so rational that nobody could deny it. Locke found it ‘as impossible to conceive that ever bare incogitative Matter should produce a thinking, intelligent being, as that nothing should produce Matter’. Mind came first, not matter. As Dan Dennett has pointed out, Locke gave an empirical, secular, almost mathematical stamp of approval to the idea that God was the designer.
Hume’s swerve
The first person to dent this cosy consensus was David Hume. In a famous passage from his Dialogues Concerning Natural Religion (published posthumously in 1779), Hume has Cleanthes, his imaginary theist, state the argument from design in powerful and eloquent words:
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 … All these various machines, and even their most minute parts, are adjusted to each other with an accuracy, which ravishes into admiration all men, who have ever contemplated them. The curious adapting of means to ends, exceeds the productions of human contrivance; of human design, thought, wisdom, and intelligence. Since, therefore the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble. [Dialogues, 2.5/143]
It’s an inductive inference, Dennett points out: where there’s design there’s a designer, just as where there’s smoke there’s fire.
But Philo, Cleanthes’s imaginary deist interlocutor, brilliantly rebuts the logic. First, it immediately prompts the question of who designed the designer. ‘What satisfaction is there in that infinite progression?’ Then he points out the circular reasoning: God’s perfection explains the world’s design, which proves God’s perfection. And then, how do we know that God is perfect? Might he not have been a ‘stupid mechanic, who imitated others’ and ‘botched and bungled’ his way through different worlds during ‘infinite ages of world making’? Or might not the same argument prove God to be multiple gods, or a ‘perfect anthropomorphite’ with human form, or an animal, or a tree, or a ‘spider who spun the whole complicated mass from his bowels’?
Hume was now enjoying himself. Echoing the Epicureans, he began to pick holes in all the arguments of natural theology. A true believer, Philo said, would stress ‘that there is a great and immeasurable, because incomprehensible, difference between the human and the divine mind’, so it is idolatrous blasphemy to compare the deity to a mere engineer. An atheist, on the other hand, might be happy to concede the purposefulness of nature but explain it by some analogy other than a divine intelligence – as Charles Darwin eventually did.
In short, Hume, like Voltaire, had little time for divine design. By the time he finished, his alter ego Philo had effectively demolished the entire argument from design. Yet even Hume, surveying the wreckage, suddenly halted his assault and allowed the enemy forces to escape the field. In one of the great disappointments in all philosophy, Philo suddenly agrees with Cleanthes at the end, stating that if we are not content to call the supreme being God, then ‘what can we call him but Mind or Thought’? It’s Hume’s Lucretian swerve. Or is it? Anthony Gottlieb argues that if you read it carefully, Hume has buried a subtle hint here, designed not to disturb the pious and censorious even after his death, that mind may be matter.
Dennett contends that Hume’s failure of nerve cannot be explained by fear of persecution for atheism. He arranged to have his book published after his death. In the end it was sheer incredulity that caused him to balk at the ultimate materialist conclusion. Without the Darwinian insight, he just could not see a mechanism by which purpose came from matter.
Through the gap left by Hume stole William Paley. Philo had used the metaphor of the watch, arguing that pieces of metal could ‘never arrange themselves so as to compose a watch’. Though well aware of Philo’s objections, Paley still inferred a mind behind the watch on the heath. It was not that the watch was made of components, or that it was close to perfect in its design, or that it was incomprehensible – arguments that had appealed to a previous generation of physicists and that Hume had answered. It was that it was clearly designed to do a job, not individually and recently but once and originally in an ancestor. Switching metaphors, Paley asserted that ‘there is precisely the same proof that the eye was made for vision, as there is that the telescope was made for assisting it’. The eyes of animals that live in water have a more curved surface than the eyes of animals that live on land, he pointed out, as befits the different refractive indices of the two elements: organs are adapted to the natural laws of the world, rather than vice versa.
But if God is omnipotent, why does he need to design eyes at all? Why not just give animals a magic power of vision without an organ? Paley had an answer of sorts. God could have done ‘without the intervention of instruments or means: but it is in the construction of instruments, in the choice and adaptation of means, that a creative intelligence is seen’. God has been pleased to work within the laws of physics, so that we can have the pleasure of understanding them. In this way, Paley’s modern apologists argue, God cannot be contradicted by the subsequent discovery of evolution by natural selection. He’d put that in place too to cheer us up by discovering it.
Paley’s argument boils down to this: the more spontaneous mechanisms you discover to explain the world of living things, the more convinced you should be that there is an intelligence behind them. Confronted with such a logical contortion, I am reminded of one of the John Cleese characters in Monty Python’s Life of Brian, when Brian denies that he is the Messiah: ‘Only the true Messiah denies his divinity.’
Darwin on the eye
Nearly six decades after Paley’s book, Charles Darwin’s produced a comprehensive and devastating answer. Brick by brick, using insights from an Edinburgh education in bottom–up thinking, from a circumnavigation of the world collecting facts of stone and flesh, from a long period of meticulous observation and induction, he put together an astonishing theory: that the differential replication of competing creatures would produce cumulative complexity that fitted form to function without anybody ever comprehending the rationale in a mind. And thus was born one of the most corrosive concepts in all philosophy. Daniel Dennett in his book Darwin’s Dangerous Idea compares Darwinism to universal acid; it eats through every substance used to contain it. ‘The creationists who oppose Darwinism so bitterly are right about one thing: Darwin’s dangerous idea cuts much deeper into the fabric of our most fundamental beliefs than many of its sophisticated apologists have yet admitted, even to themselves.’
The beauty of Darwin’s explanation is that natural selection has far more power than any designer could ever call upon. It cannot know the future, but it has unrivalled access to information about the past. In the words of the evolutionary psychologists Leda Cosmides and John Tooby, natural selection surveys ‘the results of alternative designs operating in the real world, over millions of individuals, over thousands of generations, and weights alternatives by the statistical distribution of their consequences’. That makes it omniscient about what has worked in the recent past. It can overlook spurious and local results and avoid guesswork,
