I can imagine a world where God's existence would be an undeniable fact.

I can imagine a world where cities in heathen nations regularly exploded in flames for no apparent reason; a world where we could go to the Middle East and see the entrance to the Garden of Eden, locked and barred and guarded by a flaming sword, with misty green Paradise visible in the distance beyond the gates; a world where angels flew alongside planes blowing trumpets and calling on sinners to repent. I can imagine a world of miracles and spirits, where faith healers could cure severed spinal cords or regenerate lost limbs, where prophets called fire from heaven, sent rain, parted seas and multiplied loaves and fishes, where voices boomed from the sky in answer to prayers, and where the entire geologic record consisted of fossils randomly jumbled throughout strata of flood-deposited sediments. I can readily imagine a world like this.

However, we don't live in that world.

In fact, the world we live in seems to be a distinctly natural one. There are no prophets, no angels, no Garden of Eden in the Middle East, and no trace of a global flood in the geologic record. Claims of miracles invariably turn out to be either trivial, anecdotal or spurious. The sadly gullible souls who trust in the powers of faith healers often wind up worse off than they were before, even dead. The era of true divine intervention, when miracles were real and the presence of God was undeniable, seems to be always in the past, always receding further into history.

In short, the world we live in is essentially indistinguishable from one in which there is no supernatural at all.

It wasn't always this way. Once, in the ages of superstition and ignorance, the hand of God was seen to be at work everywhere. Everything humanity did not understand, which was everything, was ascribed to the inscrutable will of the Deity. Divine purpose was discerned in the cycles of life and death, health and sickness, feast and famine. Mythological stories were invented to explain seasons, eclipses, day and night. The mad were possessed by spirits; the wise were prophets guided by the divine. Demons caused disaster and tempted us into evil. Angels safeguarded us from harm. Humanity was ruled by fear of the supernatural. People crept towards the shadows, heard the rustling and scrabbling of gods just out of sight, and hurriedly drew back.

It was the scientific revolution that gave us a candle to peer into the dark. And to our very great surprise, when we illuminated the shadows, we discovered that there was nothing there - that there never had been. The scratchings in the night were nothing more than our imagination. The light of science fell upon the world and revealed that it ran according to the regularities of natural law, not to the whims of an inscrutable cosmic intelligence. The more we investigated, the more phenomena we learned were governed by changeless physical principles, not divine dictators. If there were gods running the show, they were keeping well out of sight.

This pattern has continued today, much to some believers' chagrin. Area after area of the universe has yielded to scientific investigation, and nowhere have the telltale fingerprints of a god been discerned. There are still things we do not fully understand, but even if a god was found to be responsible for one of them tomorrow, by now there isn't much left for one to do. An enormous swath of physical phenomena have been shown to occur perfectly well on their own according to the laws of physics, with no deity required to stir the pot and get things going.

Some believers have recognized this pattern and swung into action accordingly. Though one would think an all-powerful entity needs no one's protection, they have taken great pains to safeguard him. They have declared his activities ineffable, mysterious, off-limits to scientific investigation. They have protected the last few areas of darkness where a deity might be lurking as if they were the habitat of an endangered species. The pattern is unmistakable. "See! You can't explain this!" they proclaim, pointing triumphantly to places where our knowledge is incomplete, as though scientists claimed omniscience. "And you never will be able to! That proves our god is at work!" Invariably, however, someone eventually does find a way to peer into the latest patch of darkness and finds it too is empty, pushes the borders of human knowledge a little bit further and discovers there was no god hiding just beyond them. And what do the believers do - do they admit defeat and give up their god hypothesis? Of course not. At first they rail against the new discovery, fighting it with all their strength and labeling the discoverer an enemy of the faith. Then, when the evidence mounts and the knowledge becomes impossible to deny any longer, they hurriedly usher their god into the next patch of darkness, declare once again that they see his hand moving where science falters, and the pattern repeats.

This change can be witnessed, for example, in the Christian creationist movement. This movement, whose main goal is to weaken or discredit the teaching of evolution in public school science classes, began with the young-earth creationist groups which taught and believed that all species were brought into being by God in their present forms in six literal days about six thousand years ago, and that no significant change has occurred since. However, after young-earth creationism suffered a series of crushing defeats in court, the movement has taken on a new form in the guise of "intelligent design". Advocates of this new creationism include people such as biochemist Michael Behe, who largely accepts evolution and common descent but champions the proposition that certain structures within the cell - microscopic structures and enzyme cycles, little more than a few precisely arranged molecules - are too complex for evolution to have created and must be the handiwork of an intelligent being, which advocates of ID believe to be the Christian God.

This doctrine is commonly called the God of the Gaps: wherever there are gaps in scientific knowledge, God is invoked to fill them. Whatever we don't understand must be God's work, because we don't know any other way it could have happened (which is no proof, of course, that we will never understand it). This doctrine is commonly used as an argument for God's existence by fundamentalists, especially by creationists. For example, the icon of "intelligent design" creationism is the bacterial flagellum, a submicroscopic protein filament which some species of bacteria use to swim. ID advocates claim, despite some evidence to the contrary, that this is too complex to have evolved. This is a minuscule gap indeed in which to hide such a vast deity. Is this the greatest achievement of the being they claim created all the infinite universe?

Another classic example of God-of-the-Gaps reasoning can be found in an equally classic source. In the following passage, such a fallacious argument is used by, of all people, Sherlock Holmes himself:

        He walked past the couch to the open window and held up the drooping stalk of a moss-rose, looking down at the dainty blend of crimson and green. It was a new phase of his character to me, for I had never before seen him show any keen interest in natural objects.
        "There is nothing in which deduction is so necessary as in religion," said he, leaning with his back against the shutters. "It can be built up as an exact science by the reasoner. Our highest assurance of the goodness of Providence seems to me to rest in the flowers. All other things, our powers, our desires, our food, are all really necessary for our existence in the first instance. But this rose is an extra. Its smell and its colour are an embellishment of life, not a condition of it. It is only goodness which gives extras, and so I say again that we have much to hope from the flowers."
        --Sir Arthur Conan Doyle, "The Naval Treaty" (1893)

This is a God-of-the-Gaps argument because it starts with a statement of ignorance about some natural phenomenon and reasons to a positive conclusion about God - we do not know any reason that explains why flowers are brightly colored and smell sweet, therefore these features must have been created by a deity to demonstrate its benevolence toward us. However, we now know that the sweet scent and bright color of a flower do not exist purely for human enjoyment. They serve a vital purpose in the flower's life cycle, namely to attract birds and insects that transfer pollen, which carries male gametes, from the male parts of one flower to the female parts of another, thereby fertilizing the ovum and allowing the plant to reproduce. (Elementary, dear Sherlock.) Since there is no longer any reason to attribute flowers to the action of a deity, how does this affect Doyle's argument? Does this mean we no longer have any proof of the benevolence of God?

These two examples illuminate why the God of the Gaps is bad theology and worse science. Science, by definition, must rule out the supernatural; to throw up one's hands and say, "We'll never understand this, it must be a miracle" or ascribe some phenomenon to divine activity is not an explanation, but a confession of ignorance. It tells us nothing, gives no useful information and provides no jumping-off point for further research. (As this post on the Panda's Thumb puts it, it says "poof" and declares the problem, whatever it is, to be solved.) Theologians often find it just as bad, since it takes God away from an active role in creation and consigns him to the gaps, where he steadily diminishes as our knowledge grows and those gaps shrink. The evolution of the creationist movement bears witness to this: the Christian God, who started out as the ruler of the universe who made all things by his direct will, has now shrunk to such a small size that we can only find him in certain submicroscopic parts of a few microscopic life forms. Most frighteningly for theists who realize it, this raises the possibility that God will one day be entirely erased by science. If an undeniable evolutionary explanation does emerge for the bacterial flagellum, where will ID advocates have left to go? What happens if someday there are no gaps left?

Of course, in reality this will never happen. Since it is impossible for humans to ever become omniscient, there will always be gaps, no matter how vanishingly small, where a god could hide. While the sum total of our knowledge may climb asymptotically higher, it will never reach that final boundary. Whenever we discover the cause of a phenomenon, theists can pull back one more step and ask, "Well, what causes that?" Nevertheless, even if we can never become omniscient, God-of-the-Gaps theism would eventually become a pointless proposition. Long before all the gaps were finally crushed out of existence, the remaining ones would be so minuscule that assigning a god to control them would be an exercise in futility. Few believers would countenance the idea of their deity, once hailed as the almighty creator of the entire universe, dethroned by science, demoted and reduced to pushing a few atoms around in some remote corner of space.

There is an easy and reasonable way out of this which many theists have adopted. God-of-the-Gaps-style theism is a belief system that loves ignorance and fights against science and knowledge, trying to preserve the gaps in our understanding so that God will have enough to do to make his existence worthwhile. But rather than fight science, why not embrace it? Why not assume that God acts through natural mechanisms rather than ineffable miracles, and what scientists discover are merely the methods and tools he uses to create?

There is nothing logically wrong with this proposition. Indeed, it is inherently reasonable. But there is a problem with it, nonetheless.

Science must rule out the supernatural as a method of deduction, because to invoke miracles as an explanation of something gets us nowhere. But this is not to say that scientists rule out the very idea of the supernatural; it is not an a priori exclusion. There are clearly some things, such as those described at the beginning of this essay, that if we found them would force scientists to conclude the supernatural was at work. But we haven't found any such things. Science does not assume that the supernatural does not exist. It merely holds that, if it does exist, it cannot be studied scientifically. It is not the scientists' fault that we have not found anything that cannot be studied in this way.

In other words, to all appearances our universe is a natural one. There is no evidence that clearly indicates the presence of the supernatural. One might assume that there nevertheless is a supernatural god who works behind the scenes, using natural mechanisms to his own ends. This is a faith proposition and not a scientific one, as it is not falsifiable - a subtle enough deity could never in principle be ruled out. However, the problem is this: Just as there is no evidence that indicates there is no such deity, neither is there any evidence that indicates such a being exists. Why, then, should we believe in one? What arguments could a believer in this god put forward to convince an atheist?

I should make it clear that I am not attacking those theists who are mature and wise enough to set aside the idea of the God of the Gaps. I commend those believers who have the courage to reject the obviously false idea of a god who must constantly suspend his own laws and interfere in history to keep things running. But once a person has taken this step, why not take a further one? Why not be even bolder and ask why it is necessary to believe in a deity at all?

Theists sometimes ask atheists why they spend so much time and effort arguing against a god that they don't believe exists. However, this question can be reversed and applied to the theists - why do they spend so much time and effort defending their god's existence if they have faith in him? Atheists have many reasons to argue against the existence of gods - the atrocities, injustices, attempts to gain secular power and suppression of critical thinking skills carried out in their names, to name a few. We argue that, even if gods do not exist, the detrimental effects of religion on society are unmistakably real. By contrast, however, there is no obvious reason why theists should feel compelled to defend their gods. Do all-powerful entities need the protection of mere mortals? Is it possible that God's presence is not clearly indicated by the evidence after all, so that his existence is a debatable proposition?

Just so is the God of the Gaps doctrine. Once, in the days before science when humanity was ignorant of the causes of most natural phenomena, there was little choice but to explain them as the work of an intelligent but inscrutable deity. The gaps where a god could hide were huge and pervasive. That is no longer true today, but the God of the Gaps persists. When asked why we do not see God's presence in the world, apologists offer the rationalization that we do, but only in the places where science does not understand what is going on. Not only is this argument founded on ignorance, it means that God progressively shrinks to the point of insignificance as natural explanations are uncovered for more and more of these phenomena. Thus, this view is untenable. But the alternative, that God works solely through natural mechanisms, is in practice impossible to distinguish from a god that does not exist. The most rational solution is to discard this doctrine altogether and instead take up a way of life, atheism, that is testable, that has solid arguments in its favor, and that can embrace without difficulty all the findings of science. In this way, we may one day hope to clear up the last few significant areas of darkness in our knowledge and bring humanity into a new golden age of understanding and illumination.