God-of-the-gaps arguments use gaps in scientific explanation as indicators, or even proof, of God’s action and therefore of God’s existence. Such arguments propose divine acts in place of natural, scientific causes for phenomena that science cannot yet explain. The assumption is that if science cannot explain how something happened, then God must be the explanation. But the danger of using a God-of-the-gaps argument for the action or existence of God is that it lacks the foresight of future scientific discoveries. With the continuing advancement of science, God-of-the-gaps explanations often get replaced by natural mechanisms. Therefore, when such arguments are used as apologetic tools, scientific research can unnecessarily be placed at odds with belief in God.¹ The recent Intelligent Design (ID) movement highlights this problem. Certain ID arguments, like the irreducible complexity of the human eye or the bacterial flagellum, are rapidly being undercut by new scientific discoveries.

Illustrating God-of-the-Gaps

The familiar story of Isaac Newton and Pierre Simon de Laplace is a classic example of the God-of-the-gaps argument. Newton devised a mathematical equation for the force of gravity that he used to explain and predict the motions of planets with outstanding accuracy. With pencil and paper, the orbit of the planets around the sun could be calculated with great precision. But planets also have gravitational interactions with each other, not just with the sun. For example, when the Earth passes Mars in its orbit around the sun, there is a small but significant gravitational interaction between Mars and Earth. Because these tiny interplanetary interactions occur often — several times per year in many cases — Newton suspected that these gravitational perturbations would accumulate and slowly disrupt the magnificent order of the solar system. To counteract these and other disruptive forces, Newton suggested that God must necessarily intervene occasionally to tune up the solar system and restore the order. Thus, God's periodic special actions were needed to account for the ongoing stability of the solar system.

See "How is BioLogos different from Theistic Evolution, Intelligent Design and Creationism?" and "How can evolution account for the complexity of life on earth today?"

Newton also thought that God was necessary to explain how the planets all happen to be travelling around the sun in the same direction and in the same plane. His theory of gravity was entirely compatible with planetary motions in any direction and with orbits tilted at any angle to the sun. But this is not what we find. The planets travel in the same direction, and almost all of their orbits are in the same plane. The planets move around the sun like runners on a track: very orderly. Newton thought only God could have set things up so elegantly:

"The six primary Planets are revolv'd about the Sun, in circles concentric with the Sun, and with motions directed towards the same parts, and almost in the same plane. […] But it is not to be conceived that mere mechanical causes could give birth to so many regular motions. […] This most beautiful System of the Sun, Planets, and Comets, could only proceed from the counsel and dominion of an intelligent and powerful Being." ²

In both of these examples — one related to the ongoing motion of the planets and the other related to the origin of the motions — Newton is employing textbook God-of-the-gaps reasoning. Scientific theories are proposed to explain as much as possible, and then God is brought in to cover any remaining unexplained gaps in the explanation.

We now know that Newton was wrong on both counts. The gravitational perturbations that planets experience are so completely balanced that they average out to zero over time. The net result is that the planetary motions are stable; they do not deteriorate over time. And it was a straightforward application of Newton’s theory that revealed this. Newton simply had not done all the calculations to see if his intuition was right. The same was true for the orderly motion of the planets. Newton had no concept of how solar systems could form on their own or what the planetary motions would be like in naturally forming systems. Astronomy simply had not developed to this point. In the decades after Newton, astronomers discovered that solar systems form naturally from large clouds of rotating matter. Therefore, a large, slowly rotating cloud collapses under its own gravity, and it tends to flatten into something like a pancake. Saturn's rings are an interesting example where the cloud is still present. The material collects into big clumps in the plane of the pancake. After the process is completed, a collection of clumps all travelling in the same direction and in the same plane exists — just like our solar system.

Such episodes in the history of science are not unusual. In fact they are so common that the phrase God-of-the-gaps has been coined to label the process of invoking God to account for natural phenomena that is not explained by science. The dangers of such God-of-the-gaps reasoning were highlighted a century after Newton by a situation involving the French mathematician Pierre Simon de Laplace who held a bureaucratic post in Napoleon Bonaparte’s administration. Laplace was the beneficiary of a remarkable century of progress in refining and extending Newton’s laws of motion and expanding the vision of what was going on in space. As a result, he was able to write a wide-ranging text explaining the mechanics of the heavens without invoking divine intervention.

As legend goes, Laplace was questioned by Napoleon about the absence of God in his theory: "M. Laplace, they tell me you have written this large book on the system of the universe, and have never even mentioned its Creator." To this, Laplace famously replied, “I had no need of that hypothesis.” Of course, God can be still be used as a hypothesis for the existence of the universe. But because Newton had used a deficiency in scientific explanation as an argument for God’s existence, Laplace’s theory delivered an unnecessary blow to the apologetics of the time. Herein lies the danger: If gaps in scientific knowledge are used as arguments for the existence of God, what happens when science advances and closes those explanatory gaps?

Pointers to God: Fine-Tuning and the Moral Law

In the first and third chapters of The Language of God, Dr. Francis Collins mentions pointers to God that played a role in his journey to faith. One of these pointers is the fine-tuning of the universe. Fine-tuning refers to the way the basic laws of physics appear to be delicately balanced for life. This precision calls for an explanation that science cannot provide. There is a spirited debate over the meaning of fine-tuning, and some critics charge that invoking God as the fine-tuner is a return to the God-of-the-gaps. But there does not seem to be any way to explain the detailed properties of the laws of nature from within science. Fine-tuning arguments thus go beyond science into metaphysics to explain why the world that science studies has the properties that it does. Another pointer that Collins mentions, following C. S. Lewis, is the moral law. The moral law is an implicit and universal standard of ethics for humanity. Collins describes morality as a universal law, which, unlike laws such as gravity, is broken very often. Overall, the moral law is consistent with the type of behavior that is expected of products of evolution. However, as Collins points out, altruistic behavior often seems to go beyond what would be expected from the best-established processes of Darwinian evolution.³ Mathematical models developed by theorists like Martin Nowak ⁴ have established that natural selection can produce genes for altruism, but the radical self sacrifice of great saints like Mother Theresa of Calcutta seems to go beyond what the models can account for. A completely natural account of our origins may be insufficient to explain present observations of human behavior. However, if evolutionary psychology could explain human morality, or if theoretical physics could explain such perfect constants of nature, would theistic apologetics be discredited in any way?

Fine-Tuning

Unlike a God-of-the-gaps argument, the argument for fine-tuning uses science without divine action to reveal the impeccable precision of our Universe.⁵ Fine-tuning is described in terms of physical constants and the initial conditions of our universe. Fine-tuning does not try to draw attention to where science has failed, but rather emphasizes how science has revealed the intricate balance of the universe.

One might argue that science could potentially explain the origins of these delicately balanced features, but there are two important things to keep in mind. First, it is very unlikely that a scientific theory could explain away the improbabilities of our Universe without raising other improbabilities.⁶  Second, an argument for fine-tuning is unlike a God-of-the-gaps argument in that it is not intended to prove God’s existence. While it is true that the fine-tuning of the Universe adds credence to belief in a creator, such recent scientific findings could hardly be called upon as the basis or justification of the long history of theistic belief. While the fine-tuning of the Universe does indeed lead many people to consider the possibility of God’s existence, the fact that science cannot disprove God’s existence assures us that it also cannot prove it. Instead, fine-tuning can be understood as a feature of the universe that is accordant with belief in a creator. A deeper scientific explanation of these features — albeit highly unlikely — would not ruin its usefulness as a pointer to God.

Moral Law

The moral law also offers evidence that the world has evolved in a way that is consistent with the belief in a good and loving God. This remains true whether science eventually finds an account or explanation for morality. Even if a purely natural account of moral development could be found, the simple fact that morality has evolved is something that would be expected in a world created by a just and loving God.

Evolutionary theory explains selfishness in a most obvious and natural way. Altruism is far less obvious, but it can also be explained by recognizing that humans evolved in tribes that were essentially extended families with many genes in common. Imagine two tribes, one has genes to help each other even when it requires sacrifice and one does not have such genes. Which tribe will flourish? In such ways, genes for altruism can be selected by nature and spread in a population. But in its most radical form, altruism refers to situations where individuals risk their very lives to help someone they do not even know, and from whom a reciprocal benefit is unexpected or even unimaginable. This concept runs counter to the behavior expected from the best-established processes of evolution, and there are no widely accepted theories that can fully account for such examples. Some have suggested that radical altruism might perhaps be explained as misfiring —  we mistakenly go overboard in our desire to be nice. Radical altruism is currently somewhat mysterious.

As with most situations, science may someday provide an explanation for altruism. In light of that possibility, the argument from the moral law as a pointer to God is subject to the same risk of explanation as Newton’s God-of-the-gaps argument. If radically altruistic behavior is someday given a natural evolutionary explanation, it will no longer stand out as an inconsistency in evolutionary theory. However, Robert Wright argues in Non-Zero: The Logic of Human Destiny, that the evolution of altruism can be explained as an application of game theory.⁷ In Wright’s view, the deep mystery is not altruism itself, but the intriguing mathematical structures of the universe, like game theory, that can coax from the universe surprising behaviors like altruism.

Conclusion

If gaps in scientific knowledge are the basis for belief in God, then as science progresses, evidence for God’s existence continually diminishes. Fine-tuning does not rely on divine action as an explanation, but points out the striking precision of nature’s order in line with the requirements for human life, thus establishing a mysterious connection between physics and biology. As for the moral law, its use as a pointer to God can be understood in that human behavior has evolved in a way that is consistent with the idea of a good and loving creator. Belief in any moral truth rests upon the assumption of God’s existence or some other ultimate standard.

Finally, although these pointers to God should encourage one to consider God’s existence, they must not be placed at the foundation of faith. The belief in a creator and the experience of a relationship with God should not rest solely on a logical or scientific justification. But then, as Collins himself wondered, “How can such [religious] beliefs be possible for a scientist? Aren’t many claims of religion incompatible with the “Show me the data” attitude of someone devoted to the study of chemistry, physics, biology, or medicine?”⁸  

"The more I examine the universe, and the details of its architecture, the more evidence I find that the Universe in some sense must have known we were coming." — Freeman Dyson¹

"A bottom-up approach to cosmology either requires one to postulate an initial state of the Universe that is carefully fine-tuned — as if prescribed by an outside agency — or it requires one to invoke the notion of eternal inflation, a mighty speculative notion to the generation of many different Universes, which prevents one from predicting what a typical observer would see." — Stephen Hawking and Thomas Hertog²

Fine-Tuning and Pointers to God

Fine-tuning refers to the surprising precision of nature’s physical constants and the beginning state of the universe. Both of these features converge as potential pointers to a Creator. To explain the present state of the universe, scientific theories require that the physical constants of nature — like the strength of gravity — and the beginning state of the Universe — like its density — have extremely precise values. The slightest variation from their actual values results in an early universe that never becomes capable of hosting life. For this reason, the universe seems finely-tuned for life. This observation is referred to as the anthropic principle, a term whose definition has taken many variations over the years.³ 

Constants of Nature

The fine-tuning of the universe is seen most clearly in the values of the constants of nature. There are many such constants, the best known of which specify the strength of the four forces of nature: the strong nuclear force, the weak nuclear force, the electromagnetic force, and gravity. If these forces took on even slightly different strengths, the consequences for life would be devastating.⁴ Two of these in particular, the strong and electromagnetic forces, are responsible for the unusually efficient production of carbon, the element upon which all known life is based. The forces cooperate in such a way as to create a coincidental match up of energy levels, which enables the production of carbon from the fusing of three helium atoms. For three helium atoms to collide and create carbon is very unlikely, however, because under normal circumstances, the energies would not match up perfectly, and the three helium atoms would come apart before they had time to fuse into carbon. It takes a little extra time to deal with the energy mismatch. But, if there is a statistically unusual match of the energies, then the process is much faster. The slightest change to either the strong or electromagnetic forces would alter the energy levels, resulting in greatly reduced production of carbon and an ultimately uninhabitable universe. In the 1950s, Cambridge University astronomer Fred Hoyle recognized the precision of the energy match up, called carbon resonance, and made the following observation:

"A commonsense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question." ⁵

Hoyle did not mean to argue in favor of divine intervention as an answer. The scientific explanation of carbon’s development was readily accessible, although this explanation offers no insight into why the fundamental forces cooperated to produce the unusual energy match up. Hoyle’s remark should be understood as an acknowledgement of how startling it is that the universe has the exact properties that enable the existence of life.

Consider also the strength of gravity. When the Big Bang occurred billions of years ago, the matter in the universe was randomly distributed. There were no stars, planets or galaxies—just atoms floating about in the dark void of space. As the universe expanded outwards from the Big Bang, gravity pulled ever so gently on the atoms, gathering them into clumps that eventually became stars and galaxies. But gravity had to have just the right force—if it was a bit stronger, it would have pulled all the atoms together into one big ball. The Big Bang—and our prospects—would have ended quickly in a Big Crunch. And if gravity was a bit weaker, the expanding universe would have distributed the atoms so widely that they would never have been gathered into stars and galaxies. The strength of gravity has to be exactly for stars to form. But what do we mean by “exactly”? Well, it turns out that if we change gravity by even a tiny fraction of a percent—enough so that you would be, say, one billionth of a gram heavier or lighter—the universe becomes so different that there are no stars, galaxies, or planets. And without planets, there would be no life. The other constants of nature possess this same feature. Change any of them, and the universe, like Robert Frost’s traveler, moves along a very different path. And remarkably, every one of these different paths leads to a universe without life in it. Our universe is friendly to life, but only because the past fifteen billion years have unfolded in a particular way that led to a habitable planet with liquid water and rich chemistry.

There are many other finely-tuned constants of nature besides the strengths of these forces. Consider the ratio of masses for protons and electrons, as a final example. The mass of a proton is roughly 1836.1526 times the mass of the electron.⁶ Were this ratio changed by any significant degree, the stability of many common chemicals would be compromised. In the end, this would prevent the formation of such molecules as DNA, the building blocks of life.⁷ But with regard to the development of life on Earth, it is sometimes claimed that natural selection would find a way for life to develop no matter what the circumstances. In this way, nature is sometimes said to tune itself. However, the fine-tuning of carbon is even responsible for nature’s ability to tune itself to any degree. As professor Alister McGrath has pointed out:

"[The entire biological] evolutionary process depends upon the unusual chemistry of carbon, which allows it to bond to itself, as well as other elements, creating highly complex molecules that are stable over prevailing terrestrial temperatures, and are capable of conveying genetic information (especially DNA). […] Whereas it might be argued that nature creates its own fine-tuning, this can only be done if the primordial constituents of the universe are such that an evolutionary process can be initiated. The unique chemistry of carbon is the ultimate foundation of the capacity of nature to tune itself." ⁸

Initial Conditions

Fine-tuning is also evident in the "initial conditions" or the beginning state of the universe. The initial conditions of the universe include such information as the expansion energy of the Big Bang, the overall amount of matter that was present, the ratio of matter to antimatter, the initial rate of the universe’s expansion and even the degree of its entropy.

Consider the expansion rate of the Big Bang. If it was greater, so the early universe expanded faster, the matter in the universe would have become so diffuse that gravity could never have gathered it into stars and galaxies. If it was less, so the early universe expanded more slowly, gravity could have overwhelmed the expansion and pulled all the matter back into a black hole. The expansion rate was just right, so that the universe could have stars in it.

Another interesting example of a finely-tuned initial condition is the critical density of the universe. In order to evolve in a life-sustaining manner, the universe must have maintained an extremely precise overall density. The precision of density must have been so great that a change of one part in 10¹⁵ (i.e. 0.0000000000001%) would have resulted in a collapse, or big crunch, occurring far too early for life to have developed, or there would have been an expansion so rapid that no stars, galaxies or life could have formed.⁹ This degree of precision would be like a blindfolded man choosing a single lucky penny in a pile large enough to pay off the United States’ national debt.

Responses to Fine-Tuning

Needless to say, the preceding examples carry significant implications for understanding the universe. With some thought, it seems that out of an unfathomable number of possibilities, our universe is one of very few which is capable of hosting life. Consequently, many of these observations have been used as pointers to God.

Fine-Tuning vs. Irreducible Complexity

Before continuing the discussion, it is important to distinguish these pointers to God from the biological arguments of irreducible complexity, which have a similar form. Fine-tuning provides examples of how nature is able to produce the current complexity of life, and when one reflects upon the unlikelihood of these examples, it may have the potential to point to a creator. In the case of irreducible complexity, however, the argument is advanced to suggest that nature cannot account for our present state of existence without relying upon direct, miraculous, divine intervention somewhere in the process.¹⁰ While an argument of irreducible complexity would be shattered by a scientific explanation, these pointers to God are much less vulnerable to dismissal on the basis of future scientific explanations. However, pointers to God also draw attention to the splendid precision of nature’s laws towards the evolution of life.

A Lucky Accident

Not surprisingly, fine-tuning arguments unsettle those who embrace the philosophy of naturalism, since a straightforward interpretation of the evidence points in favor of an intelligent creator. Some of the naturalist responses are common and are worth mentioning here. The first amounts to a nonchalant shrugging of the shoulders. Many adherents to philosophical naturalism give a response along the following lines: Because humans exist, the laws of nature clearly must be the ones compatible with life. Otherwise, we simply wouldn’t be here to notice the fact. To argue against this line of reasoning, John Leslie makes the analogy of surviving an execution at a firing squad completely unharmed.¹¹ Here, Leslie argues that the naturalist’s argument above is analogous to saying, "Of course all of the shots missed, otherwise I wouldn’t be here to notice that I’m still alive!” A much more logical approach would be to seek out an explanation for why such an unlikely event occurred. A good scientific explanation satisfies curiosity, whereas this kind of explanation does nothing to offer any resolution.

An Inevitability

From a more scientific standpoint, it is often claimed that the theory of inflation gives an adequate explanation for such precision and balance. The theory of inflation states that in the early stages of cosmological evolution, the universe underwent a period of exponential expansion. By proposing the right kinds of inflationary models, it is possible to show that some of the examples above — most importantly the critical density of the universe — would naturally take on the appropriate values. In this way, some of the universe’s fine-tuning seems to be explained away. Whether inflation occurs is a subject of debate. However, most theoretical physicists agree that some form of inflation took place, and more importantly this phenomenon could indeed explain many examples of fine-tuning. But what is not always included in the description of these inflation theories, is the extra fine-tuning the theories themselves require. In order to produce such an enormous inflationary rate of expansion — and to result in the necessary values for our universe’s critical density — inflation theories rely upon two or more parameters to take on particularly precise values. So precise are these values that the problem of fine-tuning remains and is only pushed one step back. A second naturalist response is to suppose that the finely-tuned features of our world will someday show themselves to have been inevitable. That is, with an increase in our understanding of physics, it is possible that one day we will discover a Theory of Everything through which all other facts of physics could be explained. Such a theory might even explain why the universal constants and physical laws have to have such specific values. However, each of the finely-tuned features of our world put certain restrictions on the possibilities for the possible Theory of Everything. In the end, only a few specific theories would suffice, and this essentially results in a fine-tuning problem even for Theories of Everything.¹²

The Multiverse

There is a final response, known as the multiverse hypothesis. The multiverse hypothesis claims that there are many other universes in addition to our own. Each of these has different properties, and different values of the basic constants of physics. If the number of these universes is extremely large, it would be less surprising that one of them would happen to provide the specific conditions for life. At first glance, the proposition of many other universes sounds impressively scientific. However, one must keep in mind that the likelihood of ever being able to observe evidence of another universe is extremely remote, since it is unlikely that information could ever pass from one universe to another. Furthermore, there is no guarantee that the process which produces all of these universes would randomly set all the physical parameters in such a way that every possibility is realized. It could be that there are constraints on the characteristics of these many universes and that the production process itself would have to be fine-tuned in some way to guarantee that we get enough variety of universes to account for our remarkable cosmic home. Additional problems arise with the details of proposing a multiverse, which are enumerated in the suggested readings below.