Design and Fine-Tuning

Psalm 19 does not argue. It declares. The psalmist does not say that a careful observer may infer a Creator from the regularities of the night sky; he says the sky is already speaking, day after day, in a voice that goes out into all the earth. That is the biblical starting point for every argument from design, and it is worth noticing before we come to the arguments, because it changes what the arguments are for. In scripture, the order and beauty of creation are not a clue left for detectives. They are a testimony God gives, and people respond to it with worship or with suppression, as Romans 1 says.

The psalm also sets the limits. Its first six verses are about the sky, and its next five are about the law of the LORD, which revives the soul and makes wise the simple. The heavens tell of glory; the word of God tells of God's will. The psalm ends not with a conclusion about the universe but with a prayer: who can discern his own errors? Cleanse me from my hidden faults (19:12). No amount of starlight answers that prayer. The church has long spoken of two books, the book of nature and the book of scripture, both written by the same Author. Psalm 19 is the clearest place in the Bible where the two books lie open side by side, and it is clear about which one speaks the gospel.

Notice what the psalm does with the sun. Israel lived among peoples for whom the sun was a god, and in Babylon the sun god was also the patron of justice. Psalm 19 makes the sun a creature living in a tent that God pitched, running his course like an athlete, and then turns to the law of the LORD where a sun-hymn might praise the sun's justice. That is already an argument of a kind: the order you see does not belong to the things that display it. It points past them. In a part of the world where the sun, the moon or the great river are still treated as powers, that is exactly the use of Psalm 19 a pastor needs first.

Paul quotes Psalm 19:4 in Romans 10:18, and he applies it to the spread of the gospel: their voice has gone out into all the earth. He uses the universal witness of the heavens as a picture of the universal reach of the preached word. That is the right order. The design argument, rightly used, is a way of helping someone hear a voice that is already speaking, so that they will listen to the voice that saves.

The design argument is old. Plato and the Stoics made versions of it, and Aquinas's fifth way argues that things without understanding act for an end, as an arrow is directed by an archer. But the form most people know comes from William Paley, an Anglican clergyman, whose Natural Theology appeared in 1802. Paley opens with a walker crossing a heath who pitched his foot against a stone, and asks how it came to be there; it might, for all he knew, have lain there for ever. Then he finds a watch on the ground. He would never give the same answer, Paley says, because the watch has parts framed and put together for a purpose, to tell the time, and if they were differently shaped or arranged it would not work at all. Then Paley spends the rest of a long book on the eye, the joints, the wings of birds and the structure of plants, arguing that living things show the same marks of contrivance as the watch, only more so.

The strongest objections to that argument had already been written before Paley published, by David Hume in his Dialogues Concerning Natural Religion (1779). Hume's sceptic Philo makes several points that still matter. The analogy between a watch and the universe is weak, since we have seen watches being made but have never seen a universe being made, and we have only one universe to examine. Even if the argument worked, it would show only a designer proportioned to the effect, not an infinite one. Nothing in it shows there is one designer rather than a committee of them. And looking at the waste and suffering in nature, Philo says, the world might be the first rough attempt of some infant deity who afterwards abandoned it. Hume's point was not that the order of nature is an illusion, but that it does not take you as far as the God of the Christians.

Then came Charles Darwin. Darwin had read Paley as a student at Cambridge and admired him. In his autobiography, written for his family in 1876, he wrote: 'The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered.' On the Origin of Species (1859) proposed that variation among living things, together with the steady pressure of which variants survive and reproduce, could over long ages produce the eye, the wing and the hand without anyone designing them. Richard Dawkins, in The Blind Watchmaker (1986), put the point in Paley's own image: natural selection is a watchmaker, but a blind one, and he wrote that Darwin made it possible to be an intellectually fulfilled atheist.

Be exact about what Darwin's theory did and did not do. It answered Paley's specific argument from biological contrivance by offering a natural mechanism. It did not address why there are laws of nature at all, why they permit life, or why the universe is intelligible, and Darwin himself did not claim it did; in his later years he called himself an agnostic, not an atheist. Christians responded in different ways from the start. The Harvard botanist Asa Gray, a committed Protestant who said he accepted the Nicene Creed, argued in America that natural selection was compatible with design and could be the way God worked. The clergyman and novelist Charles Kingsley wrote to Darwin that it was just as noble a conception of God to believe he created forms capable of developing themselves, and Darwin quoted that letter, without naming him, in the second edition of the Origin. Others judged evolution incompatible with scripture. Lesson 5 of this module sets out those views at full strength. For now note only this: the end of Paley's argument was not the end of the design argument. The argument moved.

In the second half of the twentieth century, physicists began to notice something that has nothing to do with biology. The basic laws of physics contain a number of constants, quantities such as the strength of gravity, the strength of the force that binds atomic nuclei, the masses of the elementary particles, and the energy of empty space. Our theories do not tell us why these constants have the values they do; they are measured and plugged in. And when physicists calculated what a universe would be like if the constants were different, they found that in a surprising number of cases even a small change would produce a universe with no stars, no stable atoms, no chemistry, and so no life of any kind we can imagine. That observation is called fine-tuning. It is a claim of physics, and it is accepted by many physicists who do not believe in God.

The British Astronomer Royal, Martin Rees, who is not a believer, set out six such numbers in Just Six Numbers (1999). One is the proportion of mass released as energy when hydrogen fuses into helium, about 0.007. Rees argued that if it were 0.006, the nuclear bonds needed to build helium would not hold, and the universe would contain hydrogen and almost nothing else; if it were 0.008, hydrogen would have been used up early and there would be no long-lived stars like the sun and no water. Another is the cosmological constant, the energy of empty space, which drives the universe's accelerating expansion. Naive estimates from quantum theory suggest it should be vastly larger than it is, by a factor sometimes put at ten to the power of a hundred and twenty, and the physicist Steven Weinberg argued in 1987 that if it were very much larger than it is, matter would have flown apart before any galaxies formed. Geraint Lewis and Luke Barnes, two Australian astronomers, set out the case at a popular level in A Fortunate Universe (2016).

A famous story belongs here, and should be told with a caution. In 1953 the astronomer Fred Hoyle, then an atheist, predicted that the carbon nucleus must have a particular energy level, because without it stars could not make enough carbon for us to exist. Experimenters at Caltech found the level where he said it would be. Hoyle later wrote, in a 1981 article, that a common sense interpretation of the facts suggests that a superintellect has monkeyed with physics. Historians of science, among them Helge Kragh, have since argued that Hoyle's reasoning in 1953 was not as anthropic as the later retelling suggests. The prediction was real; the neat story is partly hindsight. Use it, but use it accurately.

Not every physicist agrees that the fine-tuning is as tight as it is often presented. Victor Stenger argued in The Fallacy of Fine-Tuning (2011) that if you vary several constants at once rather than one at a time, life-permitting combinations become much more common. Fred Adams showed in 2008 that stars can form across a much wider range of some constants than had been assumed. Barnes replied to Stenger at length in a 2012 review in a professional astronomy journal, arguing that most of the fine-tuning cases survive. The fair summary is that the existence of fine-tuning for life is widely accepted among physicists, that its degree in particular cases is debated, and that the most dramatic numbers quoted in sermons are often the least secure. When you use this argument, pick one or two well-documented cases and state them exactly. Do not stack up numbers you cannot source.

The argument built on these facts runs like this. The fine-tuning of the universe for life is due to physical necessity, to chance, or to design. It is not plausibly due to necessity, since nothing we know requires the constants to take these values. It is not plausibly due to chance, since the life-permitting range is so narrow. Therefore it is due to design. Robin Collins and Richard Swinburne put the same point as a comparison of probabilities: fine-tuning is far less surprising if there is a God who intends embodied, moral creatures than if there is not, and so it is evidence for God. Each premise has been attacked, and the next section gives the attacks their due.

The first reply is the anthropic principle, a name coined by the physicist Brandon Carter in 1973. In its weak form it says something undeniable: we can only observe a universe compatible with our existence as observers. If the constants were not life-permitting, nobody would be here to notice. So, the objector says, we should not be surprised to find ourselves in a fine-tuned universe; there is nowhere else we could have found ourselves. Douglas Adams put it memorably in a talk later printed in The Salmon of Doubt (2002): a puddle wakes up and marvels at how perfectly the hole it sits in fits its shape.

The philosopher John Leslie answered with an illustration in Universes (1989). You stand before a firing squad of fifty trained marksmen. They all fire, and every one misses. You should not say: of course they missed, otherwise I would not be here to wonder about it. That is true and it explains nothing. You are entitled to ask why they all missed, and the likely answers are that they were told to, or that a great many executions are going on and you happen to be the rare survivor. That is exactly the shape of the debate that follows. The weak anthropic principle explains why we do not observe a hostile universe. It does not explain why a life-permitting universe exists at all.

Leslie's second answer, many executions, is the multiverse. If there are an enormous number of universes with different constants, then some will be life-permitting by chance alone, and we will naturally find ourselves in one of them. This is not an idea invented to avoid God. Several leading theories point toward it. Inflation, the theory of a very rapid early expansion that explains several features of the cosmic background, in many versions produces an endless sequence of bubble universes. String theory appears to allow an immense landscape of possible vacuum states, an estimate of ten to the power of five hundred is often cited, and Leonard Susskind's The Cosmic Landscape (2005) argued that this, combined with the anthropic principle, explains the constants. Martin Rees himself favours a multiverse. A student who calls the multiverse a desperate atheist fantasy is not telling the truth about the physics.

There are serious replies, and they are also worth knowing exactly. Robin Collins has argued that a universe-generating mechanism capable of producing life-permitting universes would itself need finely tuned laws, so the multiverse moves the question back rather than answering it. The philosopher Ian Hacking in 1987, and Roger White in 2000, argued that inferring many universes from the fine-tuning of this one commits a version of the inverse gambler's fallacy: walking into a casino and seeing a double six, it does not follow that many dice must have been rolled that evening. Some physicists, Paul Steinhardt among them, have criticised the multiverse on scientific grounds, arguing that a theory that can produce any outcome predicts nothing. And it remains true that no other universe has been or perhaps can be observed.

Two further objections come from the other direction. Sean Carroll, in a public debate with William Lane Craig in 2014, argued that we do not know what forms life might take under other laws, so we cannot say how improbable life is; and that an all-powerful God could have made life in any universe, so fine-tuning is not what theism predicts. Philosophers including Timothy and Lydia McGrew and Eric Vestrup argued in 2001 that if each constant could in principle take any value from zero to infinity, there is no well-defined way to assign probabilities across that range, so talk of one chance in so many is mathematically confused. Theistic defenders reply that the argument can be run on the limited range our theories actually allow, and that a God who intends creatures who can study his world has reason to make a world governed by elegant, discoverable and life-permitting law. These are open questions, argued on both sides by people who know the mathematics.

One more thing should be said plainly to Christians. A multiverse would not be a defeat for theism. Nothing in scripture says God made only one physical universe, and some Christian philosophers, Robin Collins and Klaas Kraay among them, have argued that a God of infinite creativity might well make many. The fine-tuning argument is weakened if a multiverse is real and explains the constants. The doctrine of creation is not touched.

Fine-tuning is an argument about the laws of nature. Intelligent design, as a movement, makes a stronger and more controversial claim about living things within nature: that some biological structures cannot have arisen by unguided evolution and are best explained by an intelligent cause. Christians are divided over this, and the division is not between believers and unbelievers. It runs through the church, and both sides need to be heard at full strength.

Michael Behe, a Roman Catholic biochemist at Lehigh University, argued in Darwin's Black Box (1996) that some molecular machines are irreducibly complex: they need all their parts to work at all, so they cannot have been built up one useful step at a time. His central example is the bacterial flagellum, a rotary motor with dozens of protein parts. William Dembski, a mathematician and philosopher, argued in The Design Inference (1998) that patterns which are both highly improbable and independently specified are the signature of intelligence. Stephen Meyer, in Signature in the Cell (2009), argued that the information in DNA is best explained by a mind, because in all our experience, information of that kind comes from minds. The movement's defenders insist this is not an argument from ignorance. It is an inference to the best explanation, based on what we positively know intelligent causes do. Some prominent non-Christians have found the questions serious: the atheist philosopher Thomas Nagel named Signature in the Cell among his books of the year in 2009, and argued in Mind and Cosmos (2012) that standard materialist accounts of life and mind are probably incomplete.

The critics include many Christians. Kenneth Miller, a Roman Catholic biologist at Brown University, argued in Finding Darwin's God (1999) and elsewhere that the parts of supposedly irreducible systems have known uses on their own; a subset of the flagellum's proteins forms a working injection system in other bacteria, which suggests how the motor could have been assembled from parts already doing other jobs. Behe and the microbiologist Scott Minnich reply that a subset of parts with another use does not show a step-by-step path to the whole motor, and that the injection system may well be descended from the flagellum rather than the other way round. Francis Collins, who led the Human Genome Project and is an evangelical Christian, argued in The Language of God (2006) that intelligent design stakes faith on present gaps in scientific knowledge, and that as the gaps close, so does the room for God. In 2005, in Kitzmiller v. Dover Area School District, a federal judge in Pennsylvania ruled that intelligent design could not be taught as science in public school biology classes, after hearing Behe for the defence and Miller for the plaintiffs. Intelligent design advocates regard that ruling as a legal judgment about American school policy, not a scientific refutation, and they are right that a court cannot settle a scientific question.

The deepest theological worry on the critics' side has a long history. The Scottish evangelist Henry Drummond warned in the 1890s against Christians who point to gaps in scientific knowledge and fill them with God, since the gaps keep shrinking. Dietrich Bonhoeffer, in his letters from prison in 1944, urged that God should be found in what we know, not only in what we do not. The intelligent design side answers that it is not pointing to a gap but to a positive pattern, and that refusing ever to infer design in biology is a philosophical rule, methodological naturalism, which science does not prove and which Christians need not accept. Alvin Plantinga, though not an intelligent design advocate in the usual sense, has argued that Christians may legitimately ask whether the evidence is better explained with God than without.

Here is what you can say with confidence. The fine-tuning argument does not depend on intelligent design; many Christians who accept evolution fully find fine-tuning compelling, and many intelligent design advocates also use it. Biological design arguments are contested among Christian scientists who share your faith, and you should not present them to an unbeliever as settled. If a student at a university hears you claim that the flagellum proves God, and then learns that a Catholic biologist offers an account of its origin that many biologists find persuasive, you will have taught him that Christian arguments collapse when examined. Teach the disagreement honestly, and let the strength of your case rest on arguments that survive scrutiny.

If the fine-tuning argument succeeds, it shows that the laws and constants of the universe were set by a mind that intended a universe with life in it. That is significant: it is a purpose built into physics itself, not a gap in biology. It sits well with the Creator of Psalm 19 and Romans 1, whose glory and power the heavens declare. It does not show that the designer is all-powerful, since Hume's point that the argument shows only as much as the effect requires still stands. It does not show that the designer is good; the next lesson's moral argument and the module on evil take that up. It does not show the designer acts in history, has spoken, or became flesh. A deist can accept every line of it. And Darwin's challenge stands as a warning: an argument that rests on what science cannot yet explain is always one paper away from trouble, while an argument that rests on why there is a law-governed, intelligible, life-permitting universe at all is not.

Now add to the page you began in the last lesson, headed My defence of the faith. Write the fine-tuning argument in three lines, in your own words, using one example from section 3 that you can state exactly. Underneath write the multiverse objection as a physicist who held it would put it, not as a caricature. Then write your reply in no more than five sentences, and then the two sentences: This argument shows... and: It does not show...

Then go through what you wrote with a pencil and circle every word that claims more than the lesson does: proves, impossible, all scientists, never. Replace each one with a word you can defend. This is the most useful habit in apologetics. People forgive you for an argument that is modest and true; they do not forgive you, and they should not, for an argument that is impressive and false.

Finally, go outside one night this week, if the weather allows, and read Psalm 19:1-6 under the sky, aloud if you can. Then read verses 7-14 and pray the last three verses as your own prayer. The order matters. You will spend much of this module arguing that the heavens declare the glory of God. Do not forget that the psalmist's own response was to ask God to cleanse his hidden faults.