For Further Reading
4
God and Physics
John Polkinghorne
Every worldview involves a commitment to a foundational belief, which is not itself to be explained but which will provide the basis on which all subsequent forms of explanation will ultimately have to rest. No worldview can be free from such an initial commitment, for nothing comes of nothing.
In Western thinking about the nature of reality there have been two particularly influential traditions: materialism and theism. They are both still very active today, and they differ in what they treat as their assumed foundation. The unexplained brute fact of the former is the existence of matter; for the latter, the existence of a divine Creator. Which is to be chosen depends upon how intellectually satisfying its brute-fact assumption is found to be.
My contention will be that the materialist starting point is unsatisfying. The laws of nature, as modern physics has discovered them to be, have a character which is not self-contained but rather seems to point beyond them to the need for a further and deeper level of intelligibility.
The Universe Points Beyond Itself
The universe that science explores has proved to be profoundly rationally transparent to our inquiry and endowed with a deep rational beauty. It is scarcely surprising that we are able to make good sense of the world at the level of everyday experience.
Evolutionary processes may be expected to have shaped our brains so that we can cope with survival necessities. If we could not figure out that it is a bad idea to step off the top of a high cliff, then life could prove short. That is one thing, but it is quite another thing when someone like Isaac Newton comes along and, in an astonishing creative leap of the human imagination, is able to see that the same force that makes the cliff dangerous is also the force that holds the moon in its orbit around the earth and the earth in its orbit around the sun, and, by discovering the mathematically beautiful universal inverse-square law of gravity, can explain the behavior of the whole solar system. That goes far beyond anything that we need for our survival or what might be considered to be a happy spinoff from such a necessity. As Sherlock Holmes once remarked to a shocked Dr. Watson, it did not matter at all for his daily work as a detective whether the earth went round the sun or the sun went round the earth!
The insights of modern science carry us far beyond the macroscopic realm of everyday events, downward into the microscopic realm of quantum physics and upward into the cosmic realm of curved space-time. Understanding these regimes remote from mundane experience calls for counterintuitive ways of thinking quite different from those of everyday, but physicists have proved equal to the challenge. Thus the universe has proved to be deeply intelligible and profoundly transparent to scientific inquiry. This is surely a significant fact about the world, too remarkable to be accepted simply as a happy accident or a brute fact. Albert Einstein once said that the only mystery of the universe is that it is comprehensible.
Things are more mysterious than that, for it has proved time and again that mathematics provides the key to unlock the secrets of the cosmos. It is an actual technique of discovery in fundamental physics to seek theories that are expressed in terms of beautiful equations.[1] This quest for mathematical beauty is no aesthetic indulgence on the part of the physicists; it has repeatedly proved to be the case that the theories found in this way establish their claim to be describing true aspects of nature by the long-term fruitfulness of explanation that they provide. Einstein used this kind of mathematical insight to guide his formulation of general relativity. Paul Dirac, one of the founding figures of quantum theory, made his many discoveries by a lifelong and highly successful quest for beautiful equations. His most celebrated discovery made in this way was the relativistic equation of the electron (engraved on his memorial tablet in Westminster Abbey). It immediately provided an unanticipated explanation of why the magnetic properties of the electron are twice as strong as classical physics would have led one to expect. Two years later it led to the discovery of the existence of antimatter.
When the abstract subject of mathematics leads to important physical discoveries in this way, something remarkable is happening. Why is it the case that some of the most beautiful patterns that the mathematicians can dream up in their minds are found actually to occur in the structure of the physical world around us? What links together the reason within (mathematical thinking) and the reason without (the laws of physics)? Dirac’s brother-in-law Eugene Wigner, who himself won a Nobel Prize for physics, put the matter epigrammatically: “Why is mathematics so unreasonably effective?”
It would be intolerably intellectually lazy just to shrug one’s shoulders and say, “That’s just the way it is—and a bit of good luck for those who are good at math.” Science has found that the universe is profoundly rationally transparent and beautiful. The feeling of wonder at the marvelous order of the world is a fundamental experience in physics and a fitting reward for all the labor involved in research. In a word, one could say that physics explores a universe that is shot through with signs of mind. Thus the laws of physics seem to point beyond themselves, calling for an explanation of why they have this rational character. It is intellectually unsatisfying simply to treat them as brute fact.
The deep intelligibility of the cosmos can itself be made intelligible if behind its marvelous order is indeed the mind of its Creator. The theist can say that science is possible precisely because the universe is a creation and scientists are creatures made in the image of their Creator, the God whose role is not simply to initiate the big bang but continuously to hold in being a world endowed with wonderful rational structure. Materialism just does not explain enough.
A Finely Tuned Universe
The laws of physics have been found to point beyond themselves in another way as a result of an increasing understanding of the history of the cosmos. The observable universe started 13.7 billion years ago in an extremely simple form—just an almost uniform expanding ball of energy. Now it is very rich and varied, the home of saints and scientists. Cosmologists understand many of the processes by which this fertile evolution has occurred, and they have found that they were only possible because the laws of physics—the given physical fabric of the world—took a very precise, “finely tuned” form. Carbon-based life can evolve only in a universe that has a remarkably specific character. While life did not appear on the cosmic scene until the universe was about ten billion years old, fine-tuning meant that the cosmos was pregnant with the potentiality for life essentially from the big bang onward.
Many considerations have led to this conclusion; it is possible here to give only an illustrative sample of them. Let us start with the formation of the chemical elements essential for life. The very early universe, for the first three minutes of its life, was a kind of cosmic hydrogen bomb, sufficiently hot for nuclear reactions to be taking place everywhere. When expansion cooled it below the relevant temperature, these reactions ceased, having made only the two simplest elements, hydrogen and helium. They have too boring a chemistry to be able to produce anything as interesting as life. For that many more elements are needed, including especially carbon, which is essential for the formation of the long chain molecules that are the biochemical basis of life.
After about a billion years, when the first stars had condensed, nuclear reactions started up again, now confined to hot stellar cores. These are the sites where carbon was made; every atom of carbon in every living being was once inside a star. We are people of stardust, made of the ashes of dead stars. The processes by which the heavier elements are made from a beautiful and delicate chain of nuclear reactions—essentially successively compounding a-particles (helium nuclei) step by step to form the sequence beryllium, carbon, oxygen . . .
There is a problem about the second step, however, since beryllium is very unstable and in the ordinary way would not survive long enough to enable the next reaction (forming carbon) to take place. This process is possible only because there is a very large enhancement effect (resonance) at precisely the right energy to enable the addition of the next a-particle to take place anomalously rapidly, catching the beryllium before it disappears. If the laws of nuclear physics were a little different, this resonance would either not be there at all or it would be at the wrong energy.
This chain of reactions inside the star cannot get beyond iron, the most stable of the nuclear species. Thus two problems remain: to make the elements beyond iron—some of which, such as zinc and iodine, are needed for life—and to get the elements already made out of the star and into the environment where eventually they can form part of a life-bearing planet. It turns out that with the nuclear forces in the form that they actually take in our universe, both of these problems are solved by some stars exploding as supernovae.
Another essential condition for a life-bearing universe is that it should neither expand too rapidly, becoming too dilute for fertile processes to take place, nor expand too slowly so that gravity causes it to collapse long before life can evolve. Avoiding these twin disasters requires an extremely fine balance between expansive and gravitational effects in the very early universe. Almost all cosmologists believe that this balance was achieved in our universe by a speculative but very plausible process called inflation, a kind of extremely rapid “boiling” of space which over a very short period had the effect of producing the necessary balance. This is a natural process, but it requires that the laws of physics take a particular form to enable it (technically, that they incorporate certain scalar fields called inflatons).
We have already seen how getting the right sort of stars is essential for a life-bearing universe. The character of stars depends very sensitively on the balance between two of the basic forces of nature: electromagnetism and gravity. If that balance were different to only a tiny degree in one direction or another, all stars would be either blue giants or red dwarfs. The blue giants would be short-lived in comparison with the time-scales relevant to the evolution of life, and in any case, it is thought that they would be unlikely to form planets. The red dwarfs would probably be too feeble to support life on an encircling planet, and in any case, they would never explode as supernovae, an event whose indispensability we have already noted.
One final example of fine-tuning must suffice. It has recently been discovered that the expansion of the universe is accelerating, an effect which is attributed to a somewhat mysterious entity: dark energy, associated with space itself. Quantum physics can suggest a possible source of this energy: the vacuum is the lowest energy state of the system, but it is not an empty state in which nothing is happening. (Heisenberg’s uncertainty principle does not permit a totally quiescent state in which one would know both what is happening—nothing—and where it is—here.) Instead there are continuous vacuum fluctuations in which entities appear and disappear in restless activity. This generates a vacuum energy that fills space. A reasonable estimate of the magnitude of this vacuum energy yields an enormously high figure; the observed dark energy is 10-120 smaller than this estimate. Were it not fine-tuned to this astonishing degree, the universe would have either blown apart or collapsed (depending upon the sign of the energy) with an incredible rapidity which would totally have eliminated any possibility of life forming.
Physicists agree that our universe is characterized by a precise quantitative specificity which has been necessary for its being able to evolve carbon-based life. This specificity refers to the physical fabric of the cosmos, the given ground rules which are the prior basis for the possibility of any actual events. The collection of insights on which this conclusion rests has often been given the name of the anthropic principle—a somewhat unfortunate term; the carbon principle would have been a better choice, since it is the potentiality for carbon-based life in general, rather than homo sapiens in particular, which is involved.
Fine-tuning came as a surprise to all physicists and as a shock to some. The inclination of scientists is toward the general rather than the particular. The natural prior expectation was that our universe would be just a typical specimen of what a universe might be like, with nothing too special about it. Fine-tuning seemed a counter-Copernican insight: humans do not live at the center of the universe, but the cosmos has been found to be intrinsically structured in a way that permits human presence within it. Of course, if that had not been the case, we would not be here to be astonished at fine-tuning. Yet the collection of anthropic insights seems altogether too remarkable and precise to be treated as just a happy accident. It seems to point beyond the brute fact of physical law and require to be set in a context of deeper intelligibility. Two metascientific possibilities have been extensively discussed.
The Multiverse
For the theist, the universe is not just “any old world.” It is a creation which has no doubt been endowed by its Creator with just the finely tuned laws and circumstances which have enabled it to have the fruitful history which is the expression of the divine purpose.
Disliking the threat of theism, some scientists have sought an alternative explanation of apparent fine-tuning. This is provided by the conjecture of the multiverse, a grossly extended form of naturalism which supposes that this universe is just one member of a vast portfolio of separate worlds, each with its own different laws and circumstances. If this collection is sufficiently large and varied, it might be that one of these universes is fine-tuned for carbon-based life, and that is ours because we are carbon-based life. Our fertile universe is then simply a random winning ticket in some great multiversal lottery.
Of course, if this explanation is to have any force, there must be some independent reason for believing in the existence of the multiverse. Otherwise, any remarkable feature whatsoever could be explained away by incorporating it in some arbitrary assembly, a significant needle concealed in a meaningless haystack. The collateral arguments in support of the multiverse have relied mostly on speculative versions of quantum cosmology which may seem to suggest the generation of many different worlds. At present there is no fully worked out physical theory consistently combining quantum theory and gravity, but many believe that string theory represents the most promising candidate.
In evaluating this proposal, it is important to recognize how speculative much of contemporary fundamental physics has come to be, relying solely on mathematical possibility, without the complementary input of constraining empirical results. The string theorists purport to tell us how nature behaves on a scale sixteen orders of magnitude beyond anything of which we have direct knowledge. So great a change of scale would take one from the size of a town of a hundred thousand inhabitants to much less than the size of an atom, an immense extrapolation. For this reason, the multiverse must be classified as a metascientific approach to the issue of fine-tuning.
There are also many technical difficulties in evaluating the consistency and effectiveness of the multiverse theory as far as fine-tuning is concerned. For example, simply having an infinite collection of entities is no guarantee that it will contain one with any particular property. There are an infinite number of even integers, but one will never be found with the property of oddness. Materialism may be driven to the multiverse hypothesis in order to cope with fine-tuning, but theism finds an unforced explanation already available within its overall worldview.
God and Physics in the Twenty-First Century
The twentieth century saw a significant change in the character of the account that physics gives of the processes of the universe. Classical physics of the Newtonian type visualized individual hard atoms (possibly with hooks), interacting in a determinate manner in the container of absolute space and in the course of the unfolding of absolute time. This picture was not substantially changed when the discoveries of Michael Faraday and James Clerk Maxwell led in the nineteenth century to the formulation of field theories. Classical fields are strictly deterministic in their behavior and, though not directly visible, they are clearly perceptible from their effects, as when iron filings line up along the lines of force of a magnetic field. In a word, the physical world was still thought to be clear and determinate, mechanical in its character.
All this changed in the first quarter of the twentieth century with the discoveries of relativity theory and quantum theory. Space and time were found to be intimately interrelated and their description to be dependent on the motion of the observer, while subatomic processes were found to be cloudy and fitful in their character. Mere mechanism had died with the discovery of intrinsic unpredictabilities present in the processes of nature.
Later in the century, the discovery of chaos theory showed that even the classical Newtonian world was not free of intrinsic unpredictability, for there are many systems in it which are so exquisitely sensitive to the slightest disturbance from their environment that their future behavior is beyond the possibility of detailed prediction. The word intrinsic is important here: these are not unpredictabilities that could be removed by more exact measurement or more precise calculation. Unpredictability is an epistemic property; it implies that we cannot know what future behavior will be. A fundamental problem in philosophy, and perhaps the central question in the philosophy of science, involves what connection there may be between epistemology (what we can know) and ontology (what is the case). The answer will not be determined by science alone, for it is a matter requiring metaphysical decision.
For example, quantum physics is certainly probabilistic, but does this feature arise from necessary ignorance of all the factors that actually fully determine what will happen, or is it due to an intrinsic indeterminacy in nature? In fact, it has turned out that, as far as science is concerned, either answer can be given. There are deterministic and indeterministic interpretations of quantum theory which lead to exactly the same empirical consequences. The choice between them has to be made on philosophical grounds, such as naturalness of explanation, rather than scientific criteria.
I claim that the same metaphysical options are open in the interpretation of chaotic unpredictabilities. The fact that mathematically chaos theory arose from studying the properties of deterministic nonlinear equations does not settle the issue, since these classical equations are known to be only approximations and not an exact and true account. Scientists are instinctively realists, believing that what we know is a reliable guide to what is the case—that is, that science is actually telling us what the world is like. For them it should be perfectly appropriate metaphysically to interpret the intrinsic unpredictabilities as signs of a degree of causal openness in nature. To do so is not to suppose that the future is some random lottery but that there are additional causal factors that bring it about, beyond the exchanges of energy between constituents that have been physics’s traditional story.
Taking this view is encouraged further by a new development beginning to take place in science. Instead of decomposing systems into their component parts, it has become possible to investigate the detailed behavior of modestly complex systems, treated in their totalities. It has been found time and again that dissipative systems, held far from thermal equilibrium by the exchange of energy and entropy with their environment, prove capable of spontaneously generating astonishing patterns of large-scale orderly behavior of a kind that is wholly unforeseeable in terms of constituent properties. As someone once said, “More is different”; the whole exceeds the sum of its parts.
A new kind of physics, complexity theory, seems to be on the scientific horizon, though it has not yet been properly formulated in any general kind of way. Its outline character, however, seems clear. It will be holistic rather than constituent, and its focus will be not on localized inputs of energy but on the overall patterns in which energy flows. The latter could be described by what one might appropriately call “information.” It seems reasonable to expect that by the end of the twenty-first century some well-defined concept of information will have become as central in physics as energy has been for the last 150 years. The causal concept of active information, a top-down influence of the whole upon the parts, is a strong candidate for one of the extra principles that serve to determine the future. This prospect is made more attractive by the faint but suggestive analogy between active information and the exercise of agency, a fundamental experience of human persons, who have surely always known as well as they have known anything that they are not mechanical automata. The duality of energy-information is not wholly unlike the much more profound duality of matter-mind.
Physics has certainly not proved the causal closure of the world in its own reductionist terms. This conclusion is further supported by recognition of the patchiness of much of physics’s account, with connections between different regimes not at all well understood. For example, it is not possible to combine quantum theory and chaos theory in a consistent synthesis, since quantum theory has an intrinsic scale, set by Planck’s constant, while the fractal character of chaotic dynamics implies that it is scale free, appearing the same on whatever scale it is sampled. One may take physics with all the due seriousness that it deserves without being driven to deny our human capacity to act as intentional agents. And the theist cannot be forbidden to believe that God has chosen to interact providentially with unfolding history, within the open grain of cosmic process that modern science has discerned.
God, Evolution and Quantum Theory
The potentiality present in the laws of nature has been turned into actuality in the course of the 13.7 billion years of cosmic history by a variety of evolutionary processes. While the biological evolution of life on earth is the most familiar of these scenarios, evolutionary process has also been of great significance for the physical structure of the universe. In the course of the first billion years of cosmic history, the initial almost uniform ball of matter-energy turned into a world that became grainy and lumpy with stars and galaxies. Where there had been a little more matter than average, there was an additional gravitational attraction, which then drew in further matter in a kind of snowballing process. In this way the initial small inhomogeneities were enhanced to produce ultimately a starry universe.
The essence of any evolutionary process is an interplay between contingent variations (in this case, small fluctuations of matter density in the early universe) and lawful regularity (in this case, the force of gravity). A slogan way of expressing this is to talk about chance and necessity. It is important to recognize that in this phrase “chance” is by no means a sign of meaninglessness but stands for the contingent particularity of what actually happens. Even in the course of 13.7 billion years, only a tiny fraction of what could have happened has actually taken place. The formation of stars and galaxies illustrates the general scientific insight that regimes in which true novelty emerges are always “at the edge of chaos,” where order and openness, chance and necessity are interwoven. Too far on the orderly side of that frontier, and things are too rigid for the emergence of anything really novel to be possible; too far on the haphazard side of the frontier, and no novelty that does emerge will be able to persist.
The theist has no need to be worried by the widespread role of evolutionary process. God is the ordainer of nature, and God acts as much through natural processes as in any other way. Commenting on Charles Darwin’s great discovery of biological evolution, his contemporary Charles Kingsley said that we had been shown that God had not made a ready-made world but had done something cleverer than that, making a world in which creatures “could make themselves.” Chance is simply creation’s shuffling exploration of divinely given fertility, by means of which potentiality is made actual. The theist will see the twin roles of chance and necessity as the gifts to creation of both independence and reliability, by a God who is both loving and faithful.
The physicist may well see this interweaving of order and openness reflected in the character of quantum physics and speculate that at the subatomic level this has been an important property in allowing the universe to be biofertile. While quantum physics is only capable of assigning probabilities for a number of possible results of a measurement, the range of these possibilities is also constrained by the actual character of the wave function describing the system. It is certainly not the case that anything might happen. The wave function itself evolves in time according to the Schrödinger equation, which is a deterministic differential equation. According to the widely accepted indeterministic interpretation of quantum theory, it is only when the definite form of the wave function is used to calculate the consequences of a measurement that probabilities enter the theory. Most physicists understand measurement to be the irreversible macroscopic registration of a state of affairs in the subatomic system, and it is not necessarily associated with the direct influence of a conscious observer. In other words, surely quantum processes had actual outcomes over the many billion years of cosmic history in which there were no observers present in the universe.
The interpretation of quantum theory is still a contentious issue, with a variety of incompatible points of view being advocated, but the notion of “observer-created reality” is very much a minority position. At most, “observer-influenced reality” (in laboratory experiments affected by choices of what measurements to make) is as much as should be said.
Quantum theory has also contributed to a growing recognition that nature is deeply relational and that atomism is only part of the picture. Once two quantum entities have interacted with each other, they can retain a power of mutual influence that is not diminished by spatial separation. Acting on one here will have an immediate effect on the other, even if it is now “beyond the moon,” as we conventionally say. Einstein was the first to recognize the possibility of quantum entanglement, but he thought it was “too spooky” to be true. He considered that its prediction must show that there was something wrong with conventional quantum mechanics. However, experiments have abundantly confirmed the phenomenon. The instantaneous character of the influence conveyed does not contradict special relativity, since it turns out that it cannot be used to transmit information faster than the velocity of light. Nature, it seems, rebels against a crass reductionism: even the subatomic world cannot be treated atomistically. The theist who is a trinitarian thinker will not be surprised to learn that created reality is relational.
Finally, physicists can not only peer into the universe’s past but also foresee aspects of its future. The timescales are very long, but in the end the prediction is that it will all end badly. As far as the earth is concerned, in about five billion years the sun will have consumed all its hydrogen fuel. It will then turn into a red giant, burning to a frazzle any life then left on the earth. By then life might well have migrated elsewhere in the galaxy; that, however, would only be a temporary reprieve. Over immensely long timescales, the universe itself will die, most probably by continuing to expand and becoming ever colder and more dilute. Carbon-based life will certainly prove to have been a transient episode in the history of the universe.
Eventual futility lies at the end of science’s “horizontal” story, extrapolating physical process into the distant future. However, theism has a different, “vertical” story to tell, based on the everlasting faithfulness of God. For the religious believer, the last word lies not with death but with God. That is a conviction that goes beyond anything that physics can speak about, either for or against.
For Further Reading
Holder, Rodney. God, the Multiverse and Everything. Aldershot, U.K.: Ashgate, 2004.
Polkinghorne, John. Belief in God in an Age of Science. New Haven: Yale University Press, 1998.
———. Quantum Theory: A Very Short Introduction. Oxford: Oxford University Press, 2002.
———. Quantum Physics and Theology. New Haven: Yale University Press, 2007.
Smolin, Lee. The Trouble with Physics. London: Allen Lane, 2006.