Mc Nair Lecture Chapel Hill, UNC March 23, 1993

Religion in an Age of Science

John Polkinghorne

Queens' College, Cambridge

I have spent most of my working life as a theoretical physicist and all of my consciously remembered life as part of the worshipping and believing community of the Church, so that I am someone who wants to take absolutely seriously the possibility of religious belief in a scientific age. If that belief is to be embraced with integrity, then I think two conditions must be fulfilled:

(1) We must take account of what science has to tell us about the pattern and history of the physical world in which we live. Of course, science itself can no more dictate to religion what it is to believe that religion can prescribe for science what the outcome of its inquiry is to be. The two disciplines are concerned with the exploration of different aspects of human experience: in the one case, our impersonal encounter with a physical world that we transcend; in the other, our personal encounter with the One who transcends us. They use different methods: in the one case, the experimental procedure of putting matters to the test; in the other, the commitment of trust which must underlie all personal encounter, whether between ourselves or with the reality of God. They ask different questions: in the one case, how things happen, by what process?; in the other, why things happen, to what purpose? Though these are two different questions, yet, the ways we answer them must bear some consonant relationship to each other. If I assure you that my purpose is to create a beautiful garden and then I tell you that how I am going to do so is by covering the ground with six inches of green concrete, you will rightly doubt the genuineness of my intentions. The fact that we now know that the universe did not spring into being ready made a few thousand years ago but that it has evolved over a period of fifteen billion years from its fiery origin in the Big Bang, does not abolish Christian talk of the world as God's creation, but it certainly modifies certain aspects of that discourse.

(2) We must understand that religious belief, just like scientific belief, is motivated understanding of the ways things are. Of course, a religious stance involves faith, just as a scientific investigating starts by commitment too the interrogation of the physical world from a chosen point of view. But faith is not a question of shutting one's eyes, gritting one's teeth, and believing the impossible. It involves a leap, but a leap into the light rather than the dark. It is open to the possibility of correction, as God's ways and will become more clearly known.

Scientists do not ask, 'Is that reasonable?', as if we knew beforehand what the world is going to be like. They know that when we move into regimes far away from everyday experience, all sorts of surprising things can happen. Common sense will not be the measure of all things. We are not clever enough to see very far ahead. Therefore, the scientific question is ' What makes you think this might be the case?'. A different question, you see, from 'Is that reasonable?' - a question that is open to the possibility of enlarging our understanding of how things are. Let me give you an example of the surprises that the physical world has proved to have in store for us. If I were to say to you, 'Bill is at home and he is either drunk or sober', you would expect either to find Bill at home drunk or to find him at home sober. It seems trivial and obvious; the learned would say that you have used the distributive law of logic. Oddly enough, the corresponding argument applied to a quantum world is found to obey a different kind of logic. May the same not also be true of encounter with divine reality?

In explaining my Christian belief in the setting of an Age of Science, I know it has to be motivated belief, based on evidence that I can point to. The centre of my faith lies in my encounter with the figure of Jesus Christ, as I meet him in the gospels, in the witness of the church and in the sacraments. Here is the heart of my Christian faith and hope. Yet, at a subsidiary but supportive level, there are also hints of God's presence which arise from our scientific knowledge. The actual way we answer the question 'How?', turns out to point us on the pressing also the question 'Why?', so that science by itself is found not to be sufficiently intellectually satisfying. I want to spend the rest of this lecture sketching these encouragements to religion that are available to us in our Age of Science.

A characteristic of scientific thought is the drive for synthesis. We want to have as unified an understanding as we possibly can. That is the drive behind the present activity in my old subject, particle physics, which is looking for a grand unified theory - a GUT, as we say in our acronymic way. So it's the instinct of a scientist to seek as economic and as extensive an understanding as possible, a unified understanding of the world. I believe, actually, that the grandest unified theory that you could ever conceivably reach is a theological understanding of the world. Theology is the drive to find the most profound and most comprehensive understanding of our encounter with reality. Now, if we're going to look for such a total theory, there are basically two strategies that are possible, for if we are looking for a total explanation we won't get it for nothing. Every explanation depends upon certain basic unexplained assumptions. Ex nihilo nihil fit, nothing comes from nothing. That's true intellectually, and, therefore any theory of the world will have to have its basic assumptions on which the rest of the understanding is built. There are basically two strategies corresponding to two different choices of hat you regard as fundamental, (and so not to be explained). Firstly, you can just take the brute fact of the physical world as your starting point. That's what somebody like David Hume would take. Start with the brute fact of matter as your unexplained bases. Or secondly, you can take the brute fact (if that's the word to use) of God. In other words, one can appeal to the will of an Agent, the purpose of a Creator, as the basic unexplained starting point for understanding the world. The first approach is the strategy of atheism. The second approach is the strategy of theism. I want to defend the second strategy and to explain to you why I believe that, if we are driven be the desire to have as comprehensive and unified an understanding as possible, we shall find it in a scheme of things that has a place for belief in God.

If we were to start with the brute fact of the physical world. that world is described for us at least in part by the laws of science. Therefore, if that's going to be a satisfactory starting place for us, we would have to feel intellectually satisfied with those laws as being a comfortable intellectual resting place, the foundation on which to build the rest of our understanding. The first important point I want to make is to suggest that in fact if we take the laws of nature as discerned by science seriously, and if we look at them carefully, we will find that they are not sufficiently intellectually satisfying in themselves alone. They are not sufficiently self explanatory to be comfortable resting places, or a natural given foundation for our belief. They seem to have a certain character, which I am going to describe, which actually points beyond themselves. In other words, out of the scientific understanding of the world, arise questions which seem to direct us beyond science itself to a deeper level of intelligibility, Here are two examples.

The first example is a fact about the physical world which is very familiar to us, a fact indeed that makes science possible. Most of the time we take it simply for granted, but, if we stop to think about it, I think we'll see that it is not a fact that we should accept without further thought. It is simply this: that we can understand the physical world, that it is intelligible to us in its rational transparency. Not only is that so, but it is the case that it is mathematics which is the key to the understanding of the basic structure of the physical world. It is an actual technique in theoretical physics, a technique that has proved its value time and again in the history of the subject, to look for theories which in their mathematical expression are economic and elegant. In other words, we seek theories which have about them that unmistakable character of mathematical beauty. It is our expectation that it is precisely those theories with that character of mathematical beauty which will prove to be the ones that describe the structure of the world in which we live.

If you have a friend who is a theoretical physicist and you wish to upset him or her, you simply say to them, 'That latest theory of yours looks rather ugly and contrived to me'. They will be very upset, because you are saying to them 'It doesn't have that indispensable character of mathematical beauty'. When we use mathematics in that way, as a key to unlock the secrets of the universe, something very peculiar is happening. You see - what is mathematics? Mathematics is the free exploration of the human mind. Our mathematical friends sit in their studies, and out of their heads they dream up the beautiful patterns of mathematics. If mathematics is not your subject, just think of mathematics as being a pattern-creating, pattern-analyzing subject. What I'm saying is that some of the most beautiful patterns thought up by the mathematicians are found actually to occur in the structure of the physical world around us. In other words, there is some deep-seated relationship between the reason within (the rationality of our minds - in this case mathematics) and the reason without (the rational order and structure of the physical world around us). The two fit together like a glove. If you stop to think about it, I think you'll see that is a rather significant fact about the world. It's a fact about the world that the mathematicians, in their very modest way of speaking, would describe as non-trivial. Non-trivial is a mathematical word meaning highly significant! Not only does it strike me as significant, but it also struck Einstein that way, which is perhaps more interesting. Einstein once said, "The only incomprehensible thing about the universe is that it is comprehensible". Why are our minds so perfectly shaped to understand the deep patterns of the world around us?

You have a choice in these matters. You can always just shrug your shoulders and say, 'Well, that's just the way it happens to be, and a bit of good luck for you chaps who are good a mathematics'. My instincts as a scientist, as someone who is searching for understanding, is not to be as intellectually lazy as that. I want to ask the question a famous theoretical physicist called Eugene Wigner once asked, Hey is mathematics so unreasonably effective in understanding the physical world?'. You might reply, 'Why pretty easy - evolutionary biology will explain that for you'. If our minds didn't fit the world around us, we just wouldn't have survived in the struggle for existence. Now, that's obviously true, but it's only true up to a point. It's true about our experience of the everyday world of rocks and trees where we have to dodge the rocks and miss the trees, and it's true of our mathematical thinking of the world, which I suppose amounts to a little elementary arithmetic and a little elementary Euclidean geometry. But, when I'm talking about the power of mathematics to illuminate and give understanding of the physical world, I'm not talking just about the everyday world. I'm talking, for example, about that counter-intuitive, unpicturable quantum world. That is a world that we can't visualize, bit we can understand it, and, for its understanding we need very abstract mathematics, ultimately the mathematics of spontaneously broken, gauge-field theories - which I'm sure you'll agree is fairly abstract mathematics!

Paul Dirac invented something called quantum field theory which is fundamental to our understanding of the physical world. I can't believe Dirac's ability to invent that theory, or Einstein's ability to invent the general theory of relativity, is a sort of spin-off from our ancestors having to dodge sabre-toothed tigers. It seems to me that something much more profound, much more mysterious is going on. I would like to understand why the reason within and the reason without fit together at a deep level. Religious belief provides me with a entirely rational and entirely satisfying explanation of that fact. It says that the reason within and the reason without have a common origin in this deeper rationality which is the reason of the Creator, whose will is the ground both of my mental and my physical experience. That's for me an illustration of theology's power to answer a question, namely the intelligibility of the world, that arises from science bit goes beyond science's unaided power to answer. Remember, science simply assumes the intelligibility of the world. Theology can take that striking fact and make it profoundly comprehensible.

You could summarize what I have said so far by saying that when we look at the rational order and transparent beauty of the physical world, revealed through physical science, we see a world shot through with signs of mind. And, to a religious believer it is the Mind of the Creator that is being discerned in that way. That's one example of how I think our thirst for understanding will take us beyond science and will make science itself, or the brute fact of the physical world, by itself and unsatisfactory intellectual resting place.

Let me give you another example, a scientific discovery of a more specific character that's been made in the last thirty or forty years. We thought a little earlier about the fact that we live in a universe that's had a very interesting history. It started about fifteen billion years ago and it started extremely simple. One of the reasons why cosmologists can talk with great confidence about the very early universe is that the very early universe is so simple, just an expanding ball of energy. Yet, the world that started so simple has become very rich and complex through its evolving history, with you and me as the most interesting consequences of that history known to us. We are the most complicated physical systems that we have ever encountered in our explorations of the world. So, the history of the universe has been astonishingly fruitful, and we understand many steps in that evolving, fruitful process. When we think about those steps and our understanding of them, we reach a very surprising conclusion.

Scientists can play intellectual games, and they play those games with a serious intent. The sort of game they play is this: when we think of the universe we live in, it is characterized by certain types of scientific laws and certain types of basic forces that go with those laws. For example, we live in an universe which has gravity in it, not just any old gravity, but gravity of a particular type and a particular strength. There is an intrinsic strength to the force of gravity built into the fabric of our universe, into the specification of what sort of world we live in. In fact, it's a very weak force, the way we measure things. That might surprise you if you have ever walked out of a second story window, but the force of gravity is intrinsically very weak. Now we can play intellectual games and say, 'I wonder what the universe would be like, and what its history would have been like, if gravity had been a bit different - if it had been much stronger, or even a little bit weaker than it is'. And we can play similar games with all the other fundamental forces of nature. We can take electromagnetism, the force that holds matter together. You can sit on your chairs because electromagnetism holds them together, and it holds you together as well! We can again say, 'What would the universe be like if electromagnetism were weaker, or if it were stronger?' and so on. We can play these intellectual games and, when we do that, a very surprising conclusion follows. Unless the fundamental physical laws were more or less precisely what they actually are, the universe would have had a very boring and sterile history. In other words, it's only a very special universe, a finely-tuned universe, a universe in a trillion, you might say, which is capable of having had the amazingly fruitful history that has turned a ball of energy into a world containing you and me. This insight is called the anthropic principle: a world capable of producing anthropoi, (complicated consequences comparable to men and women) is a very special finely-tuned universe. It's a very surprising discovery!

Let me illustrate why we think that's so. If you are to have a fruitful universe, one of the things you've got to have in it are stars. And, you've got to have stars of the right sort. The stars have two jobs that are absolutely indispensable to the fruitful history of the universe. One is, they have to act as long-term, steady energy sources. Essentially all our energy here on earth comes from the sun, either directly or indirectly through fossil fuels. The sun has been burning steadily for about five billion years and it will continue to burn steadily for about another five billion years more. You need that for the development of life. You must have long-term energy sources, because it takes billions of years for life to develop, and you must have steady energy sources, because stars that flared up or died down would either burn life to a frazzle or freeze it to death. So you must have what we call main sequence stars which are steadily-burning, long-lived stars. Now, we understand what makes them burn in that sort of way. Basically it's the balance between the force of gravity and the electromagnetic forces. If you were to alter either of those forces, you would put the stars out of kilter. You'd have stars that either burned up very rapidly, that lived just for millions of years rather than billions of years, or you'd have stars that were very turbulent and unstable and flared up and died down, and that would be disastrous. No life could develop in a universe of that character. So you see how difficult it is to design a fruitful universe. You've got to get the right balance between gravity and electromagnetism to make the stars act as acceptable energy sources for like. But that's only part of the story, because the stars have another tremendously important thing to do. The nuclear furnaces that burn inside the stars are the source of the chemical elements which are the raw materials of life. The early universe is very simple, and because the early universe is very simple it only produces very simple consequences. In fact, the very early universe can only make the two simplest chemical elements, namely hydrogen and helium. And they are just not rich enough in their chemistry to make life possible. For life you need a much more complicated chemistry than hydrogen and helium by themselves could sustain. In particular, you need the chemistry of carbon, which has the ability to make those immensely complicated macro-molecules which are the basis of the possibility of life. Every atom of carbon inside your body was once inside a star. We're all made from the ashes of dead stars. The only place you can make those heavier elements which are indispensable as the constituents of life is inside the right sort of stars, and it's pretty difficult to make the stars do that. Think about it. What you have to do is this: first you've got to make carbon by making three helium nuclei stick together. That's actually quite hard to do and it depends upon very delicate aspects of the nuclear forces. Now, suppose you've figured out how to do that. You can't sit back and feel satisfied, because carbon is not enough. You've got to make lots more elements. You've got to make oxygen for example. That means making another helium atom stick to the carbon you already made and turn the carbon into oxygen. But, wait a minute. You've got to do that, but you must not overdo it. You mustn't turn all the carbon into oxygen otherwise you've lost the carbon. So, you've got to get all these balances right , and so on, and so on, up to iron. If you can just tune the nuclear forces right, you can make all the elements up to iron inside the stars, but iron is the most stable of all the nuclear species and you can't get beyond iron inside the stars. So, you've still got two problems left that you've got to solve. One is you'll need to make some of the heavier elements beyond iron, some way or another, and you also have to make accessible for life the elements you've already made. It's no good making carbon, oxygen, and all that, and leaving them locked up, useless, inside the cooling core of a dying star. You'll have made the elements, but they won't be of any use to bring about life. You've got to make sure that your stars are such that when they come to the end of their natural life, which is about ten billion years, some of them will explode as supernovae and so will scatter out into the environment those chemical elements that they've made. If you're make from stardust, there's got to be some dust from stars around for you to be made of. You've got to have stellar explosions. And, if you're very clever, you can arrange in the explosion that the neutrinos, as they blow-off the outer layer of the star, then make those heavier elements like lead and so on that you couldn't make inside the star itself. The details don't matter very much, but I hope I've given some feeling that making elements is a very complicated process, which depends for its fruitfulness on a very delicate, fine-tuned balance between the nuclear forces that control these processes. If those nuclear forces were in any way slightly different from the way they actually are, the stars would be incapable of making the elements of which you and I are composed. That gives you some idea how difficult it is to make a fruitful universe. There are many, many other considerations of that kind.

I'll move on to ask the question, 'What do we make of that?'. What do me make of the fact that the world we live in is only fruitful because it's given basic scientific constitution is of a very special, very finely-tuned character. Once again, you can shrug your shoulders and say, 'Well, that's just the way it happens to be. We're here because we're here and that's it'. That doesn't seem to me to be a very rational approach to the issue. I have a friend, John Leslie, who is a philosopher at Guelf University in Canada, and he writes about these questions. He has written far and away the best book about the anthropic principle, called Universes. He's a beguiling philosopher because he does his philosophy by telling stories, which is a very accessible way for those of us who are not professionally trained in philosophy to get the hang of it. He tells the following story. You are about to be executed. Your eyes are bandaged and you are tied to the stake. Twelve highly-trained sharp shooters have their rifles levelled at your heart. They pull the trigger, the shots ring out - you've survived! What do you do? Do you shrug your shoulders and say, 'Well, that's the way it is. No need to seek and explanation of this. That's just the way it is'. Leslie rightly says that's surely not a rational response to what's going on. He suggests that there are only two rational explanations of that amazing incident. One is this. Many, many, many executions are taking place today and just by luck you happen to be the one in which they all miss. That's the rational explanation. The other explanation, is, of course, that the sharp shooters are on your side and they missed by choice. In other words there was a purpose at work of which you were unaware.

You see how that parable translates into thinking about a finely-tuned and fruitful universe. One possibility is that maybe there are lots and lots of different universes, all with different given physical laws and circumstances. If there were lots and lots of them (and there would really have to be rather a lot) then just by chance, in one of them, the laws and circumstances will be such as to permit the development of carbon-based life. But, of course, that's the one in which we live, because we couldn't appear anywhere else. It's a possible explanation that's called the many-universes interpretation. The other possibility that there is more going on than has met the eye and the sharp shooters are on our side. That translates into the idea that this is not just any old universe. Rather it is a universe which is a creation which has been endowed by its Creator with just those finely-tuned given laws and circumstances that will make its history fruitful. It is the fulfillment of a purpose.

Leslie says in relation to the anthropic principle that there is an even-handed choice between those two possibilities. By itself, I think that is correct. Let me emphasize that both are metaphysical explanations. We have no adequate, scientific motivation for thinking of any other universe but the universe of our direct experience. So the speculation that there are many, many other universes is a metaphysical speculation. I'm not against metaphysics. In fact, you can't live without it, but the many-universes interpretation is a metaphysical speculation just as the existence of a Creator is a metaphysical speculation. Of course, if you think there are other reasons, as indeed I do, for believing that there is a God whose will and purpose lies behind the universe, then that second explanation, that the world is fruitful because it is a creation, becomes the more economic and persuasive explanation. That, of course, is the one to which I myself adhere.

So, in the intelligibility of the world and the finely-tuned fruitfulness of the world, we see insights arising from science, but calling for some explanation and understanding which, by its very nature will go beyond what science itself can provide. And that shows to me, at any rate, the insufficiency of a merely scientific view of the world. In fact, I think we're living in an age where there is a great revival of natural theology taking place. Natural theology is the attempt to learn something about God by the general use of reason and by inspection of the world. That revival of natural theology is taking place, not on the whole among the theologians, who have rather lost their nerve in that area, but among the scientists. Ant not just among pious scientists like myself, who would be rather inclined to think that way, but among scientists who have no particular time for, or understanding of, conventional religion, bit who, nevertheless, feel that the rational beauty and the finely-tuned fruitfulness of the world suggest that there is some intelligence or purpose behind the universe which is more than has met the scientific eye. That revived natural theology is also revised in the sense that it is more modest in its ambitions. Unlike either the natural theology of the late middle ages or the eighteenth century, it doesn't claim to talk about proofs of God. We're in an area of discourse, of the search for understanding, where knock-down argument or proof is not available to anyone. But we are in an area where we're looking for insights which are intellectually satisfying. I wouldn't want to say that atheists are stupid, but I would want to say that atheism is less intellectually satisfying and less comprehensive in the understanding it provides, than is a theistic view of the world.

That's part of the story and these are gifts that theology gives to science. It offers science a deeper, more comprehensive understanding than would be obtained from itself alone. But there is traffic across the border in both directions and I'll spend a few moments talking about hat I think are the gifts that science to theology in this Scientific Age. That kind of gift is rather different - for it is to tell theology what the physical world is actually like in its structure and in its history. That raises issues to which theology has to address itself.

Let me begin by saying just a word about what many people think is the classic interaction between science and theology, namely the question of origins. How did things begin? Actually I don't think that's a very important subject, and that people are mistaken if they think it is. They are in error because they wrongly think that the theological doctrine of creation is concerned with how things began. Who lit the blue touch paper of the big bang? The doctrine of creation isn't about that. It's not concerned with temporal origin, but with ontological origin. It answers the question, why do things exist at all? God is as much the Creator today as he was fifteen billion years ago. Thus though big bang cosmology is very interesting scientifically, theologically it is insignificant. Therefore, if my friend and former colleague Steve Hawking comes along, as he does in his book, A Brief History of Time,and says that if you think about quantum cosmology and how quantum mechanics fuzzed out the very early universe, then, though the universe has a finite age, it has no dateable beginning, that's a very interesting scientific speculation, but there's no particular theological mileage in it. Steve says, 'If there is no beginning, what place then for a Creator?'. It is theologically naive to answer other than by 'Every place, as the Sustainer of the universe in Being'. God is not a God of the edges, with a vested interest in beginnings. God id the God of all times and all places. So I think the question of origins is not terribly important theologically, though it is certainly interesting scientifically.

Much more interesting is the question of the process of the world. How does the world history unfold? It is in sustaining the fruitful process of the world that God is at work as the Creator, as much today as he was fifteen billion years ago. When we think about the process of the world, we get two insights that come to us from science which we have to take seriously and to think about. The first is this. I've talked about that very fertile process which turned a ball of energy into a world containing you and me. I've said that it could only happen in a very special, finely-tuned sort of universe. Let's now go on to ask the question: Given we've got a universe with fine-tuning (given we've got the right ground rules) how does it actually come about that the world makes itself? How does it realize its in-built fruitfulness, its in-built potentiality? We understand many bits of that process quite well. All those bits we do understand seem to realize that fruitfulness through an interplay between two opposing tendencies which, in a sort of slogan-way, we could describe as 'chance' and 'necessity'. Those are slippery words and I have to explain what I mean by them. By 'chance', I mean simply happenstance - just the way things happen to be. When the universe was about a billion years old, there just happened to be a little bit more matter here than there. That was chance - happenstance - getting things going. That happenstance produced something lasting through the operation of 'necessity', that is to say, lawful regularity. Because, if there is a little bit more matter here than there, then that matter exerts a little bit stronger gravitational pull, ant it draws more matter to itself in a sort of snowballing process. That's how we picture the universe, which started so uniform, began to get a bit grainy and lumpy, and essential step in its fruitful history. You've got to have the stars and you've got to have the galaxies that contain the stars. A fruitful universe has to become lumpy at some stage. That begins through chance, happenstance, and develops through necessity, snowballing through the attractive force of gravity. And, it seems that the interplay between those two tendencies, chance as the origin of novelty, and necessity as the sifter and preserver of the novelty thus produced, is the prime way in which the fruitfulness of the universe is realized. A much more familiar example is provided by biological evolution. Mutations occur through happenstance. That produces some new possibility for life, which is then sifted and preserved in the lawfully regular environment which is necessary for the operation of natural selection. In every stage of the fruitful history of the universe there is an interplay between chance and necessity. Now, the question is, 'What do we make of that?'

A very great French biochemist called Jacques Monod wrote a famous book in the early 1970's whose English translation is called Chance and Necessity. And, in that book, Monod says, with passionate Gallic rhetoric, 'Pure chance, absolutely free, but blind lies at the basis of this stupendous edifice of evolution'. Of course the word where Monod puts in the knife is the word 'blind'. For Monod, the role of chance, of happenstance, in the evolving history of the universe subverts the religious claim that there is a purpose at work in the world. For Monod, the role of chance means that ultimately the universe is a tale told by an idiot. That's how he sees it.

Here is a serious challenge which we have to address. I would approach it this way. There is no unique way of going from physics to metaphysics, from science to a deeper view. I will take the same scientific picture of the interplay between happenstance and regularity, but offer an alternative interpretation of it and, I would venture to say, a more evenhanded interpretation, which lays as much emphasis on the necessary half as upon the chance half of the process. I respectfully suggest that when God came to create the world he was faced with a dilemma. The Christian God is a God of love and the gift of love is always the gift of independence, the genuine otherness of the beloved. Parents know that. There comes a time when Johnny has to be allowed to ride his bicycle into dangerous traffic on his own. The gift of love is a gift of a true independence. So, a God who is loving will endow his creation with its own due freedom, its own due independence. But, independence by itself can easily degenerate into simply licence and chaos. However God is not only loving, he is faithful. And the God who is faithful will surely endow his creation also with the gift of reliability. Yet reliability by itself can easily rigidify into a merely mechanical world. I believe that the Christian God, who is both loving and faithful, has given to his creation the twin gifts of independence and reliability, which find their reflection in the fruitful process of the universe through the interplay between happenstance and regularity, between chance and necessity. That would be my re-interpretation of this insight into the fruitful physical process.

There is a second thing I want to say, and it's this: many people have a picture of the physical world which is very outdated. The great triumphs of the science in the eighteenth century, and the further discoveries of the nineteenth century, encouraged a view of the physical world as if it were in some sense mechanical, a rather rigid and deterministic world. Actually, we've always known that can't be right, because we've always known as an absolutely basic fact of human nature that we have the experience of choice and responsibility. In the twentieth century we have made further scientific gains and twentieth-century science has seen the death of a merely mechanical view of the world. In part, that is due to the cloudy fitfulness of quantum theory lurking at the atomic and sub-atomic roots of the world. But I think, more importantly still, it is also due to another unexpected insight of science gained in the last thirty - forty years. Even the physics of the everyday world, even the physics of Newton, is not as mechanical as Sir Isaac and his followers would have thought it to be. That's a very surprising discovery. Those of us who learned classical physics, learned the subject by thinking about certain tame, predictable systems, like a steadily ticking pendulum. That's a very simple robust system. If you take a pendulum and slightly disturb it, or you are slightly ignorant about how it is moving, the slight disturbance only produces slight consequences, the slight ignorance only produces slight errors in your estimation of how it will behave. We thought the everyday Physical world was all like that. It was tame, it was predictable, it was controllable - in a word, it was mechanical. Now, we've discovered that, in fact, almost all the everyday physical world is not like that at all. Almost all of the everyday physical world is so exquisitely sensitive that the smallest disturbance produces quite uncontrollable and unpredictable consequences. There are very many more clouds than clocks around. This is the insight that is rather ineptly named chaotic dynamics. It came as a very great surprise to us. It is not altogether astonishing that the discovery was first made in relation to attempts to make models of the earth's weather systems. In the trade it is sometimes called the butterfly effect: that the great weather systems of the earth are so sensitive to individual circumstance that a butterfly stirring the air with its wings in Beijing today will have consequences for the storm systems over London in a month's time. Now, that world - that exquisitely sensitive world - is an intrinsically unpredictable world. We can't know about all those butterflies in Beijing. So we've learned that the physical world, whatever it is, it certainly isn't mechanical, even at the everyday level. It is something more subtle and more supple than that. To do justice to the full development of the argument, I'd need to say a good many more things, but I think already one can see the beginnings of a picture of the physical world that is unpredictable in detail and open to the future. That is a gain for science. Science begins to describe a world which is sufficiently flexible in its development, a world of true becoming, of which we can consider ourselves as inhabitants. The future is genuinely new, not just a rearrangement of what was there in the past. In such a world of true becoming, with its open future, we can begin to understand our own powers of agency, our own powers to act and bring things about. I would want to say also that such a physical world is one which, in my view, is capable also of being open to God's providential interaction and his agency in the world. So that whole picture of the physical world has been loosened up. It is much more hospitable to the presence of both humanity and divine providence than would have seemed conceivable a hundred years ago.

It is time for me to come to an end. I'd like to finish with a quotation which in many ways summarizes for me what I'm trying to do in my own intellectual exploration as someone who is both a physicist and a priest. You see, I want to hold these two parts of me together, not without puzzles, of course, but I hope, without dishonesty, and without compartmentalism. I don't want to be a priest on Sundays and a physicist on Mondays. I've tried this evening to show one or two examples of how science and theology interact positively to help each other, how religious belief is possible with integrity in an Age of Science. So let me end with one of my favourite quotations from a great Thomist thinker of this century, Bernard Lonergan. He once said this: 'God is the all sufficient explanation, the eternal rapture glimpsed in every Archimedean cry of eureka'. I like that very much. The search for understanding, which is so natural to a scientist is, in the end , the search for God. That is how religion will continue to flourish in this Age of Science.
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