The Science of Discworld III - Darwin's Watch

2. PALEY'S WATCH

THE SCENE: A RADIO CHAT-SHOW in the Bible Belt of the United States, a few years ago. The host is running a phone-in about evolution, a concept that is anathema to every God-fearing southern fundamentalist. The conversation runs something like this: HOST: So, Jerry, what do you think about evolution? Should we take any notice of Darwin's theories?

JERRY: That Darwin guy never got a Nobel Prize, did he? If he's so great, how come he don't get no Nobel?

HOST: I think you have a very good point there, Jerry.

Such a conversation did occur, and the host was not being ironic. But Jerry's point is not quite the knock-down argument he thought it was. Charles Robert Darwin died in 1882. The first Nobel Prize was awarded in 1901.

Of course, well-meaning people are often ignorant about fine points of historical detail, and it is unfair to hold that against them. But it is perfectly fair to hold something else against them: the host and his guest didn't have their brains in gear. After all, why were they having that discussion? Because, as every God-fearing southern fundamentalist knows, virtually every scientist views Darwin as one of the all-time greats. It was this assertion, in fact, that Jerry was attempting to shoot down. Now, it should be pretty obvious that winners of Nobel prizes (for science) are selected by a process that relies heavily on advice from scientists. And those, we already know, are overwhelmingly of the opinion that Darwin was somewhere near the top of the scientific tree. So if Darwin didn't get a Nobel, it couldn't have been (as listeners were intended to infer) because the committee didn't think much of his work. There had to be another reason. As it happens, the main reason was that Darwin was dead.

As this story shows, evolution is still a hot issue in the Bible Belt, where it is sometimes known as 'evilution' and generally viewed as the work of the Devil. More sophisticated religious believers - especially European ones, among them the Pope - worked out long ago that evolution poses no threat to religion: it is simply how God gets things done, in this case, the manufacture of living creatures. But the Bible-Belters, in their unsophisticated fundamentalist manner, recognise a threat, and they're right. The sophisticated reconciliation of evolution with God is a wishy-washy compromise, a cop-out. Why? Because evolution knocks an enormous hole in what otherwise might be the best argument yet devised for convincing people of the existence of God, and that is the `argument from design'[5].

The universe is awesome in its size, astonishing in its intricacy. Every part of it fits neatly with every other part. Consider an ant, an anteater, an antirrhinum. Each is perfectly suited to its role (or 'purpose'). The ant exists to be eaten by anteaters, the anteater exists to eat ants, and the antirrhinum ... well, bees like it, and that's a good thing. Each organism shows clear evidence of `design', as if it had been made specifically to carry out some purpose. Ants are just the right size for anteaters' tongues to lick up, anteaters have long tongues to get into ants' nests. Antirrhinums are exactly the shape to be pollinated by visiting bees. And if we observe design, then surely a designer can't be far away.

Many people find this argument compelling, especially when it is developed at length and in detail, and `designer' is given a capital `D'. But Darwin's `dangerous idea', as Daniel Dennett characterised it in his book with that title, puts a very big spoke into the wheel of cosmic design. It provides an alternative, very plausible, and apparently simple process, in which there is no role for design and no need for a designer. Darwin called that process `natural selection'; nowadays we call it `evolution'.

There are many aspects of evolution that scientists don't yet understand. The details behind Darwin's theory are still up for grabs, and every year brings new shifts of opinion as scientists try to improve their understanding. Bible-Belters understand even less about evolution, and they typically distort it into a caricature: `blind chance'. They have no interest whatsoever in improving their understanding. But they do understand, far better than effete Europeans, that the theory of evolution constitutes a very dangerous attack on the psychology of religious belief. Not on its substance (because anything that science discovers can be attributed to the Deity and viewed as His mechanism for bringing the associated events about) but on its attitude. Once God is removed from the day-to-day running of the planet, and installed somewhere behind DNA biochemistry and the Second Law of Thermodynamics, it is no longer so obvious that He must be fundamental to people's daily lives. In particular, there is no special reason to believe that He affects those lives in any way, or would wish to, so the fundamentalist preachers could well be out of a job. Which is how Darwin's lack of a Nobel can become a debating point on American local radio. It is also the general line along which Darwin's own thinking evolved - he began his adult life as a theology student and ended it as a somewhat tormented agnostic. Seen from outside, and even more so from within, the process of scientific research is disorderly and confusing. It is tempting to deduce that scientists themselves are disorderly and confused. In a way, they are - that's what research involves. If you knew what you were doing it wouldn't be research. But that's just an apology, and there are better reasons for expecting, indeed, for valuing, that kind of confusion. The best reason is that it's an extremely effective way of understanding the world, and having a fair degree of confidence in that understanding.

In her book Defending Science - Reason the philosopher Susan Haack illuminates the messiness of science with a simple metaphor, the crossword puzzle. Enthusiasts know that solving a crossword puzzle is a messy business. You don't solve the clues in numerical order and write them in their proper place, converging in an orderly manner to a correct -solution, unless, perhaps, it's a quick crossword and you're an expert. Instead, you attack the clues rather randomly, guided only by a vague feeling of which ones look easiest to solve (some people find anagrams easy, others hate them). You cross-check proposed answers against others, to make sure everything fits. You detect mistakes, rub them out, write in corrections.

It may not sound like a rational process, but the end result is entirely rational, and the checks and balances - do the answers fit the clues, do the letters all fit together? - are stringent. A few mistakes may still survive, where alternative words fit both the clue and the words that intersect them, but such errors are rare (and arguably aren't really errors, just ambiguity on the part of the compiler).

The process of scientific research, says Haack, is rather like solving a crossword puzzle. Solutions to nature's riddles arrive erratically and piecemeal. When they are cross-checked against other solutions to other riddles, sometimes the answers don't fit, and then something has to be changed. Theories that were once thought to be correct turn out to be nonsense and are thrown out. A few years ago, the best explanation of the origin of stars had one small flaw: it implied that the stars were older than the universe that contained them. At any given time, some of science's answers appear to be very solid, some less so, some are dubious ... and some are missing entirely.

Again, it doesn't sound like a rational process, but it leads to a rational result. Indeed, all that cross-checking, backtracking, and revision increases our confidence in the result. Remembering, always, that nothing is proved to the hilt, nothing is final.

Critics often use this confused and confusing process of discovery as a reason to discredit science. Those stupid scientists can't even agree among themselves, they keep changing their minds, everything they say is provisional - why should anyone else believe such a muddle? They thereby misrepresent one of science's greatest strengths by portraying it as a weakness. A rational thinker must always be prepared to change his or her mind if the evidence requires it. In science, there is no place for dogma. Of course, many individual scientists fall short of this ideal; they are only human. Entire schools of scientific thought can get trapped in an intellectual blind alley and go into denial. On the whole, though, the errors are eventually exposed - by other scientists.

Science is not the only area of human thought to develop in this flexible way. The humanities do similar things, in their own manner. But science imposes this kind of discipline upon itself more strongly, more systematically, and more effectively, than virtually any other style of thinking. And it uses experiments as a reality check.

Religions, cults, and pseudoscientific movements do not behave like that. It is extremely rare for religious leaders to change their minds about anything that is already in their Holy Book. If your beliefs are held to be revealed truth, direct from the mouth of God, it's tricky to admit to errors. All the more credit to the Catholics, then, for admitting that in Galileo's day they got it wrong about the Earth being the centre of the universe, and until recently they got it wrong about evolution.

Religions, cults and pseudoscientific movements have a different agenda from science. Science, at its best, keeps lines of enquiry open. It is always seeking new ways to test old theories, even when they seem well established. It doesn't just look at the geology of the Grand Canyon and settle on the belief that the Earth is hundreds of millions of years old, or older. It cross-checks by taking new discoveries into account. After radioactivity was discovered, it became possible to obtain more accurate dates for geological events, and to compare those with the apparent record of sedimentation in the rocks. Many dates were then revised. When continental drift came in from left field, entirely new ways to find those dates arrived, and were quickly used. More dates were revised.

Scientists - collectively - want to find their mistakes, so that they can get rid of them.

Religions, cults, and pseudoscientific movements want to close down lines of enquiry. They want their followers to stop asking questions and accept the belief system. The difference is glaring. Suppose, for instance, that scientists became convinced that there was something worth taking seriously in the theories of Erich von Daniken, that ancient ruins and structures must have been the work of visiting aliens. They would then start asking questions. Where did the aliens come from? What sort of spaceships did they have? Why did they come here? Do ancient inscriptions suggest one kind of alien or many? What is the pattern to the visitations? Whereas believers in von Daniken's theories are satisfied with generic aliens, and ask no more. Aliens explain the ruins and structures - that's cracked it, problem solved.

Similarly, to early proponents of divine design and their modern reincarnations creationism and `intelligent design', the latest quasireligious fad, once we know that living creatures were created (either by God, an alien, or an unspecified intelligent designer) then the problem is solved and we need look no further. We are not encouraged to look for evidence that might disprove our beliefs. Just things that confirm them. Accept what we tell you, don't ask questions.

Ah, yes, but science discourages questions too, say the cults and religions. You don't take our views seriously, you don't allow that sort of question. You try to stop us putting our ideas into school science lessons as alternatives to your world view.

To some extent, that's true - especially the bit about science lessons. But they are science lessons, so they should be teaching science. Whereas the claims of the cults and the creationists, and the closet theists who espouse intelligent design, are not science. Creationism is simply a theistic belief system and offers no credible scientific evidence whatsoever for its beliefs. Evidence for alien visitations is weak, incoherent, and most of it is readily explained by entirely ordinary aspects of ancient human culture. Intelligent design claims evidence for its views, but those claims fall apart under even casual scientific scrutiny, as documented in the 2004 books Why Intelligent Design Fails, edited by Matt Young and Taner Edis, and Debating Design, edited by William Dembski and Michael Ruse. And when people (none of the above, we hasten to point out) claim that the Grand Canyon is evidence for Noah's flood - a notorious recent incident - it's not terribly hard to prove them wrong.

The principle of free speech implies that these views should not be suppressed, but it does not imply that they should be imported into science lessons, any more than scientific alternatives to God should be imported into the vicar's Sunday sermon. If you want to get your world view into the science lesson, you've got to establish its scientific credentials. But because cults, religions and alternative belief systems stop people asking awkward questions, there's no way they can ever get that kind of evidence. It's not only chance that is blind. The scientific vision of the planet that is currently our only home, and of the creatures with which we share it and the universe around it, has attained its present form over thousands of years. The development of science is mostly an incremental process, a lake of understanding filled by the constant accumulation of innumerable tiny raindrops. Like the water in a lake, the pool of understanding can also evaporate again - for what we think we understand today can be exposed as nonsense tomorrow, just as what we thought we understood yesterday is exposed as nonsense today. We use the word `understanding' rather than, `knowledge' because science is both more than, and less than a collection of immutable facts. It is more, in that it encompasses organising principles that explain what we like to think of as facts: the strange paths of the planets in the sky make perfect sense once you understand that planets are moved by gravitational forces, and that these forces obey mathematical rules. It is less, because what may look like a fact today may turn out tomorrow to have been a misinterpretation of something else. On Discworld, where obvious things tend to be true, a tiny and insignificant Sun does indeed revolve round the grand, important world of people. We used to think our world was like that too: for centuries, it was a `fact', and an obvious one, that the Sun revolved round the Earth.

The big organising principles of science are theories, coherent systems of thought that explain huge numbers of otherwise isolated facts, which have survived strenuous testing deliberately designed to break them if they do not accord with reality. They have not been merely accepted as some act of scientific faith: instead, people have tried to falsify them - to prove them wrong - but have so far failed. These failures do not prove that the theory is true, because there are always new sources of potential discord. Isaac Newton's theory of gravitation, in conjunction with his laws of motion, was - and still is - good enough to explain the movements of the planets, asteroids and other bodies of the solar system in intricate detail, with high accuracy. But in some contexts, such as black holes, it has now been replaced by Albert Einstein's theory of general relativity.

Wait a few decades, and something else will surely replace that. There are plenty of signs that all is not well at the frontiers of physics.

When cosmologists have to postulate bizarre `dark matter' to explain why galaxies don't obey the known laws of gravity, and then throw in even weirder `dark energy' to explain why galaxies are moving apart at an increasing rate, and when the independent evidence for these two powers of darkness is pretty much non-existent, you can smell the coming paradigm shift.

Most science is incremental, but some is more radical. Newton's theory was one of the great breakthroughs of science - not a shower of rain disturbing the surface of the lake, but an intellectual storm that unleashed a raging torrent. Darwin's Watch is about another intellectual storm: the theory of evolution. Darwin did for biology what Newton had done for physics, but in a very different way. Newton developed mathematical equations that let physicists calculate numbers and test them to many decimal places; it was a quantitative theory. Darwin's idea is expressed in words, not equations, and it describes a qualitative process, not numbers. Despite that, its influence has been at least as great as Newton's, possibly even greater. Darwin's torrent still rages today.

Evolution, then, is a theory, one of the most influential, farreaching and important theories ever devised. In this context, it's worth pointing out that the word `theory' is often used in a quite different sense, to mean an idea that is proposed in order to be tested. Strictly speaking, the word that should be used here is `hypothesis', but that's such a fussy, pedantic-sounding word that people tend to avoid it. Even scientists, who should know better. `I have a theory,' they say. No, you have a hypothesis. It will take years, possibly centuries, of stringent tests, to turn it into a theory.

The theory of evolution was once a hypothesis. Now it is a theory. Detractors seize on the word and forget its dual use. `Only a theory,' they say dismissively. But a true theory cannot be so easily dismissed, because it has survived so much rigorous testing. In this respect there is far more reason to take the theory of evolution seriously than any explanation of life that depends on, say, religious faith, because falsification is not high on the religious agenda. Theories, in that sense, are the best established, most credible parts of science. They are, by and large, considerably more credible than most other products of the human mind. So what these people are thinking of when they chant their dismissive slogan should actually be `only a hypothesis'.

That was a defensible position in the early days of the theory of evolution, but today it is merely ignorant. If anything can be a fact, evolution is. It may have to be inferred from clues deposited in the rocks, and more recently by comparing the DNA codes of different creatures, rather than being seen directly with the naked eye in real time, but you don't need an eyewitness account to make logical deductions from evidence. The evidence, from several independent sources (such as fossils and DNA), is overwhelming. Evolution has been established so firmly that our planet makes no sense at all without it. Living creatures can, and do, change over time. The fossil record shows that they have changed substantially over long periods of time, to the extent that entirely new species have arisen. Smaller changes can be observed today, over periods as short as a year, or mere days in bacteria.

Evolution happens.

What remains open to dispute, especially among scientists, is how evolution happens. Scientific theories themselves evolve, adapting to fit new observations, new discoveries, and new interpretations of old discoveries. Theories are not carved in tablets of stone. The greatest strength of science is that when faced with sufficient evidence, scientists change their minds. Not all of them, for scientists are human and have the same failings as the rest of us, but enough of them to allow science to improve.

Even today there are diehards - not a majority, despite the noise they make, but a significant minority - who deny that evolution has ever occurred. Most of them are American, because a quirk of history (coupled with some idiosyncratic tax laws) has made evolution into a major educational issue in the United States. There, the battle between Darwin's followers and his opponents is not just about the intellectual high ground. It is about dollars and cents, and it is about who influences the hearts and minds of the next generation. The struggle masquerades as a religious and scientific one, but its essence is political. In the 1920s four American states (Arkansas, Mississippi, Oklahoma, and Tennessee) made it illegal to teach children about evolution in public schools. This law remained in place for nearly half a century: it was finally banned by the Supreme Court in 1968. This has not stopped advocates of `creation science' from trying to find ways round that decision, or even to get it reversed. Largely, however, they have failed, and one reason is that creation `science' is not science; it lacks intellectual rigour, it fails objective tests, and at times it is plain nutty.

It is possible to maintain that God created the Earth, and no one can prove you wrong. In that sense, it is a defensible thing to believe. Scientists may feel that this `explanation' doesn't greatly help us understand anything, but that's their problem; for all anyone can prove, it could have happened that way. But it is not sensible to follow the Anglo-Irish prelate James Ussher's biblical chronology and maintain that the act of creation happened in 4004 BC, because there is overwhelming evidence that our planet is far older than that - 4.5 billion years rather than 6000. Either God is deliberately trying to mislead us (which is conceivable, but does not fit well with the usual religious messages, and may well be heretical) or we are standing on a very old lump of rock. Allegedly, 50 per cent of Americans believe that the Earth was created less than 10,000 years ago, which if true says something rather sad about the most expensive education system in the world.

America is fighting, all over again, a battle that was fought to a fmish in Europe a century ago. The European outcome was a compromise: Pope Pius XII did accept the truth of evolution in an encyclical of 1950, but that wasn't a total victory for science[6]. In 1981 a successor, John Paul II, gently pointed out that `The Bible ... does not wish to teach how the heavens were made, but how one goes to heaven.' Science was vindicated, in that the theory of evolution was generally accepted, but religious people were free to interpret that process as God's way of making living creatures. And it's a very good way, as Darwin realised, so everyone can be happy and stop arguing. Creationists, in contrast, seem not to have appreciated that if they pin their religious beliefs to a 6000-year-old planet, they are doing themselves no favours and leaving themselves no real way out.

Darwin's Watch is about a Victorian society that never happened - well, once the wizards interfered, it stopped having happened. It is not the society that creationists are still attempting to arrange, which would be far more `fundamentalist', full of self-righteous people telling everyone else what to do and stifling any true creativity. The real Victorian era was a paradox: a society with a very strong but rather flexible religious base, where it was taken for granted that God existed, but which gave birth to a whole series of major intellectual revolutions that led, fairly directly, to today's secular Western society. Let us not forget that even in the USA there is a constitutional separation of the state from the Church. (Strangely, the United Kingdom, which in practice is one of the most secular countries in the world - hardly anyone attends church, except for christenings, weddings, and funerals - has its own state religion, and a monarch who claims to be appointed by God. Unlike Discworld, Roundworld doesn't have to make sense.) At any rate, the real Victorians were a God-fearing race, but their society encouraged mavericks like Darwin to think outside the loop, with far-reaching consequences.

The thread of clocks and watches runs right across the metaphorical landscape of science. Newton's vision of a solar system running according to precise mathematical `laws' is often referred to as a `clockwork universe'. It's not a bad image, and the orrery - a model solar system, whose cogwheels make the tiny planets revolve in some semblance of reality - does look rather like a piece of clockwork. Clocks were among the most complicated machines of the seventeenth and eighteenth centuries, and they were probably the most reliable. Even today, we say that something functions `like clockwork'; we have yet to amend this to `atomic accuracy'.

By the Victorian age, the epitome of reliable gadgetry had become the pocket-watch. Darwin's ideas are intimately bound up with a watch, which again plays the metaphorical role of intricate mechanical perfection. The watch in question was introduced by the clergyman William Paley, who died three years after Darwin was born. It features in the opening paragraph of Paley's great work Natural Theology, first published in 1802[7]. The best way to gain a feeling for his line of thinking is to use his own words: In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that for anything I knew to the contrary, it had lain there forever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, that, for anything I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case, as in the first? For this reason, and for no other, viz. that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point to the hour of the day; that if the different parts had been differently shaped from what they are, of a different size from what they are, or placed after any other manner, or in any other order, than that in which they are placed, either no motion at all could have been carried on in the machine, or none which would have answered the use that is now served by it.

Paley goes on to elaborate the components of a watch, leading to the crux of his argument: This mechanism being observed ... the inference, we think, is inevitable; that the watch must have had a maker; that there must have existed, at sometime, and at some place or other, an artificer or artificers, who formed it for the purpose which we find it actually to answer; who comprehended its construction, and designed its use.

There then follows a long series of numbered paragraphs, in which Paley qualifies his argument more carefully, extends it to cases where, for instance, some parts of the watch are missing, and dismisses several objections to his reasoning. The second chapter takes up the story by describing a hypothetical `watch' that can produce copies of itself - a remarkable anticipation of the twentieth-century concept of a Von Neumann machine. There would still be good reason, Paley states, to infer the existence of a 'contriver'; in fact, if anything, the effect would be to enhance one's admiration for the contriver's skill. Moreover, the intelligent observer would reflect, that though the watch before him were, in some sense, the maker of the watch which was fabricated in the course of its movements, yet it was in a very different sense from that in which a carpenter, for instance, is the maker of a chair.

He continues to develop this thought, and disposes of one possible suggestion: that, just as a stone might always have existed, for all he knew, so a watch might have always existed. That is, there might have been a chain of watches, each made by its predecessor, going back infinitely far into the past, so that there never was any first watch. However, he tells us, a watch is very different from a stone: it is contrived. Perhaps stones could always have existed: who knows? But not watches. Otherwise we would have `contrivance, but no contriver; proofs of design, but no designer'. Rejecting this suggestion on various metaphysical grounds, Paley states: The conclusion which the first examination of the watch, of its works, construction, and movement, suggested, was, that it must have had, for the cause and author of that construction, an artificer, who understood its mechanism, and designed its use. This conclusion is invincible. A second examination presents us with a new discovery. The watch is found, in the course of its movement, to produce another watch, similar to itself: and not only so, but we perceive in it a system or organisation, separately calculated for that purpose. What effect would this discovery have, or ought it to have, upon our former inference? What, as hath already been said, but to increase, beyond measure, our admiration of the skill which had been employed in the formation of such a machine!

Well, we can all see where the good reverend is leading, and he homes in on his target in his third chapter. Instead of a watch, consider an eye. Not lying on a heath, but in an animal, which perhaps does lie on a heath. What he does say is: compare the eye to a telescope. There are so many similarities that we are forced to deduce that the eye was `made for vision', just as the telescope was. Some thirty pages of anatomical description reinforce the contention that the eye must have been designed for the purpose of seeing. And the eye is just one example: consider a bird, a fish, a silkworm, or a spider. Now, finally, Paley states explicitly what all his readers knew was coming from page one: Were there no example in the world of contrivance except that of the eye, it would be alone sufficient to support the conclusion which we draw from it, as to the necessity of an intelligent Creator.

There we have it, in a nutshell. Living creatures are so intricate, and function so effectively, and fit together so perfectly, that they can have arisen only by design. But design implies a designer. Ergo: God exists, and it was He who created Earth's magnificent panoply of life. What more is there to say? The proof is complete.