This paper was published in Spanish in Religión y Cultura, Vol. LIII:240, Jan.-Mar. 2007, pp. 137-153.
Science studies concrete, detectable, reproducible facts, and tries to explain why they happen. This is done by means of scientific hypotheses or theories, which are more credible as a function of the number of facts they explain. These theories have predictive power: they announce the results of experiments which have not yet been performed, or the existence of phenomena not yet detected. The higher the number of correct predictions associated to a theory, the higher its credibility.
However, a fact disagreeing with the theory, or the inability to confirm a predicted result, is enough to force us to revise the theory. In the scientific method, facts have precedence above theories, although theories sometimes may be supported by correct predictions of formerly unknown facts.
A classical example is given by the theory of universal gravitation, formulated by Isaac Newton (1642-1727). When it was first proposed, back in the seventeenth century, it explained a large number of facts: from the fall of bodies in ordinary life, to the movement of heavenly bodies. One of its big successes was the mathematical deduction of the three laws induced half a century before by Johann Kepler (1571-1630), who obtained them empirically from the observation of planetary orbits.
But the big success of the theory of gravitation, what made it the indisputable basis of classical physics, was a correct prediction. In 1781, William Herschel (1738-1822) discovered Uranus, the first new planet to be added to those known since the oldest antiquity. During the following sixty years, astronomers observed carefully the orbit of Uranus and detected a slight discrepancy with respect to the theoretical orbit predicted for this planet by the theory of gravitation. There were two possibilities: either Newton's theory was not correct and should be modified, or there was an unknown fact which would make it possible to save the theory.
In 1845, the Englishman John Couch Adams (1819-1892) came to the conclusion that the problem would be solved if there were an additional planet, furthest than Uranus, whose attraction would produce the observed discrepancies. Adams was young and had no contacts. The work he sent to James Challis, director of the Cambridge observatory, suggesting him to look for the unknown planet, was ignored.
Just two months later, the French astronomer Urbain Le Verrier (1811-1877) came to the same conclusion, but being a well-known astronomer, his corresponding request to the German astronomer Johann Gottfried Galle (1812-1910) was paid attention. On September 23 1846, Galle discovered the planet proposed by Adams and Le Verrier, which was named Neptune. The success of the prediction became a first-order scientific news and gave the apparently final support to Newton's theory of gravitation.
In 1855, Le Verrier brought his attention to the orbit of Mercury, which also presented disagreements with the theory, and tried to apply the same procedure which had made him famous a few years before. The discrepancies could be explained if there were an unknown planet between Mercury and the Sun. Le Verrier suggested astronomers to try and find it, and was so certain of its discovery, that he even gave it a name: Vulcan.
During several decades, astronomers sought in vain the mysterious and elusive Vulcan. The reason for the failure had to wait until 1915. On that year, Einstein published his general theory of relativity, which corrected Newton's theory of universal gravitation and explained (among other things) most of the anomalies in the orbit of Mercury. Planet Vulcan stays now only in the science-fiction literature: in the famous TV series Star Trek, Mr. Spock declares that he was born on that planet.
A scientific theory is always provisional. You can never say that it has been finally proved. At most, you can say that it explains all the known facts, and that it has made one or more correct predictions, but one cannot exclude the possibility of a new fact being discovered which will make us refine it.
According to Karl Popper , a theory cannot be considered scientific unless it can be proved to be false, i.e. an experiment can be designed which, if successful, would break down the theory. Unfalsifiable theories are not valid scientific constructs. At most they can be hypothetical exercises, more or less elegant, without any relation to reality. John Horgan  calls these constructions ironic science.
In a previous paper  I have described how the queen of sciences, physics, is producing unfalsifiable theories who nobody can prove, with which it is leaving the field of science and getting into the field of metaphysics, a discipline which is not scientific, but philosophical. Here I will signal the same phenomenon in another experimental science: biology, which at first sight would seem less prone to these tendencies.
This question is now a current issue with regard to a supposed scientific theory (intelligent design) which several religious groups in the United States are presenting as an alternative to the theory of evolution. They are pushing to have both taught on equal grounds in the text books on natural sciences, in the first and second levels of education.
This attempt has induced the indignation of many scientists, who accuse the proponents of intelligent design of trying to slip a purely philosophical or religious theory as a scientific alternative to the theory of evolution. Although evolution, as any other scientific theory, will always be provisional, it has received enough support to make it unassailable without cause, and any attack on it should be based, not on speculations, but on disagreeing facts, which up to now have not surfaced.
The problem gets more complicated because some of the men of science who defend the theory of evolution get a step further and fall in the same sin with which they charge their opponents, presenting philosophical speculations and dogmatic statements as though they were verifiable scientific theories.
On the first place, one must ask oneself what is actually the scientific theory of evolution. The word scientific implies that this theory can only have to do with verifiable facts and hypothesis to explain them, which should always be subject to the possibility of proving that they are false. In this context, the theory of evolution is based on the verifiable observation that species change, and studies the mechanism by means of which this can happen: mutations, DNA, natural selection and so forth.
Additional philosophical connotations cannot be scientific, both if one says, with some believers, that there is an intelligent design behind everything, as in the opposite stance, that everything is the result of mere chance.
It is difficult to reach an agreement in this problem. Let us assume that there is something in living beings which is impossible to explain as an effect of chance. In that case, an atheist scientist can always say that there exists some still unknown cause which, when discovered, will explain satisfactorily the pending question. Also, the supporters of the scientific theory of intelligent design present supposed proofs, usually badly designed, based usually on the existence of very complex organs, such as the eye, or rotating flagella in bacteria, or on complicated behaviors, as wasps which paralyze spiders by injecting venom in each of their nervous ganglia. These arguments are usually presented as though they were new and unanswerable, while they actually are over a century old  and have been rejected long ago by evolutionary scientists . For instance, it is a mistake to assume that the evolutionary line towards the apparition of an eye must be the result of a gradual evolution through intermediate species with partial or imperfect visual organs, unable to perform usefully. In actual fact, the evolution of the eye can have taken place as a result of a few mutations, each of them indifferent or with selective value.
On the other hand, it is possible that everything we know about living beings may be compatible with the action of apparent chance. However, even in this case, the hypothesis of intelligent design would not be automatically excluded, for God may have included chance among the tools he has used to create the universe. Or are we going to deny God the capability of using mechanisms which we ourselves do use?
We have inklings indicating that evolution is compatible with intelligent design. In a recent branch of computer science, evolutionary programming, procedures inspired on biological evolution are applied to program building. In one of its subdivisions, artificial life, evolutionary programming is used to develop agents which remind the behavior of living beings, such as the simulation of ant colonies, which throws light on the behavior of swarms of beings who act together and let us formulate hypotheses about the emergence of higher order entities: multi-cellular organisms, or insect and human societies . Experimentation on artificial life can also be used to study the transmission of language among groups of human beings, simulated as drastically simplified agents.
Obviously, any experiment on artificial life is a case of intelligent design (by the programmer). In these experiments, agents usually interact under the control of algorithms which use series of random numbers, i.e. under the control of chance. If some day we were able to produce intelligent agents in our simulations, these agents could not deduce our existence by experimentation, as we are outside their world, and they could come to the conclusion that their world existed by mere chance: an evidently false conclusion, from our point of view. Our role with respect to them would be (saving the obvious differences) parallel to that of God with respect to our universe. In the hypothetical circumstances I have described, the atheistic metaphysical argument which states that the universe has not been created by anybody and has developed by itself as a purely random process would be false, but our agents would be unable to prove it or disprove it. It is thus evident that the same argument applied to our universe may not be valid, but we cannot prove it either. Therefore, this question is not scientific.
In summary: the scientific theory of evolution is today at the level of Newton's theory of gravitation in the nineteenth century. It explains better than any other, and with more detail, the scientific facts we know at present with respect to the origin of species. As any other scientific theory, it cannot be considered final, but we should not expect a revolution which suddenly declares it obsolete or mistaken, rather one or more fine adjustments, as those Einstein did on physics.
On the other hand, neither intelligent design, nor atheistic evolution by mere chance, is a scientific theory: both are impossible to be proved false. Therefore they are metaphysical theories and should be presented as such. Both.
Textbooks on natural sciences should not present intelligent design as an alternative to the scientific theory of evolution, because it is not. But they should not say either that science has proved that there is no God or, in a more surreptitious way, that everything in the universe is the consequence of mere chance, because those two statements are simply false: science has not proved, nor cannot prove, any of those things.
Let us make then metaphysics. Assuming that God exists, and that the universe has been the object of intelligent design, how could God act, in which way does God interact with the cosmos, to lead its development according to his design?
Obviously, God could manipulate the universe by skipping the laws He has given it, i.e. through miraculous actions. However, from the study of nature and history, it seems that this type of divine actions, if it happens, is extremely rare. God hides from us with an exquisite care. He does not appear to wish that his existence can be proved in an unassailable way. Perhaps, if He did, He would force our will, cancel our freedom. Or perhaps not. Three science-fiction authors have speculated on what would happen if God gave an indisputable proof of his existence .
Can God manipulate the universe, modify its evolution, without our knowing it? This would be a special type of divine action, which is usually called providence.
Some modern theologians have tried to explain possible modes of divine action as a function of modern scientific advances. In particular, quantum mechanics and chaos theory have been offered, the first due to the ontological indeterminism inherent in several of its interpretations, the second because it implies the impossibility of very long term predictions. We must remember, however, that all these theories are always provisional. Using them in theological explanations poses a certain amount of risk.
In a recent book , Nicholas Saunders dismantles some of these attempts, showing their inconsistencies and clarifying something we did know, or at least suspected: proving God's existence by means of science is probably impossible. Both atheism as belief in God are, and probably will always be, a question of faith, rather than science.
Since I am not a professional theologian (we are all amateur, except practical atheists), my thoughts expressed in the following paragraphs should be taken with a grain of salt. I find them useful, and so I put them forward, just in case they could be useful for somebody else.
Modern science has revolutionized our vision of the world. In the eighteenth century, Newton's theory of gravitation could be considered established, and gave rise to a materialistic-deterministic vision of the universe which can be personified in one of the most significant scientists of the time, Pierre-Simon, marquis de Laplace (1749-1827), whose fields of study covered mathematics, astronomy, chemistry and biology. The success of his studies on the dynamics of the solar system moved him to state that, if we knew the exact initial conditions of the universe, it would be possible to predict all its past and future development. This gave rise to materialistic determinism, so successful in the nineteenth century and still a part of the popular vision of the world, in spite of the three devastating attacks it has suffered during the twentieth century.
The first attack was the principle of uncertainty, formulated in 1927 by Werner Heisenberg (1901-1976). In essence, this principle denies that we can know exactly the initial conditions of a physical system at any instant in time. With this, Laplace's assumption falls down, for the principle of uncertainty excludes, as a particular case, that we can know the initial conditions of the universe.
There was a way to save a part of Laplace's hypothesis. OK, we'll never be able to know the exact initial conditions, but couldn't we know them with sufficient approximation to predict, with a reasonable accuracy, the future development of the cosmos?
The second attack (not necessarily in chronological order) demolished this hope. In 1963, in his studies on meteorology, Edward Lorenz discovered the existence, predicted a few decades before by Poincaré, of dynamic systems where an infinitesimal difference in their initial conditions gives rise to a global discrepancy in the state of the system after some time. The study of these systems is called chaos theory. On the other hand, we now know that the universe, or even a relatively small part of it, such as the solar system, is a chaotic system. So we'll never know the initial conditions of the universe with sufficient approximation, because the approximation will never be sufficient. However the number of exact figures we may know, even to the maximum allowed by the principle of uncertainty, chaos theory makes certain that, after some time (less than the age of the universe) they would be useless to allow us to do correct predictions.
The third attack was even more devastating, if possible. Quantum mechanics, developed in the nineteen twenties, states that the basic components of the universe, represented by elementary particles, are not deterministic, but random. Predicting the future of the universe is not only impossible at long range, but also in every step in its existence. Besides the deterministic chaotic macrocosm, whose exact evolution we shall never able to predict completely, we also have an intrinsically probabilistic microcosm, whose evolution can only be followed with statistics. Both things at the same time, although we still don't know how to put them together.
The material world, the object of study for science, can be represented in this paradigm of modern physics by means of a segment of a straight line, with potentially chaotic determinism at one end (dominating the macroscopic action of gravity) and intrinsic indeterminism at the other (represented by microscopic quantum mechanics).
This is the current image of the world provided by physics. At one side, an apparent determinism, actually fuzzy, because the universe is chaotic; at the other end we get indeterminism. What can we say about human freedom?
It is evident that free will, as envisioned by classical philosophers, is incompatible with determinism. But it would be a mistake to assume that therefore it has something to do with quantum indeterminism. When a radioactive atom disintegrates, it is not using freedom; rather it is subject to the suffocating influx of probability. One atom may disintegrate ten times later than another, but its longevity has not been chosen individually, it is the result of the play of blind forces which, on the average, produce the effect that one half of the atoms must disintegrate in a perfectly defined time.
Are human beings free? Obviously we are determined by many factors: our genes, the education we got, all our personal history. But at the bottom of our conscience we are convinced that, before a dilemma, we are free to choose. In fact, all the structure of our society would break down if this hypothesis were not true. Thus even the most fervid opponents of the real existence of human freedom speak and act constantly as though they believed in it.
Modern science seems to have a fixation with human freedom: it just denies its existence. Against all the fundamental tenets of the scientific method, it puts theories before facts and denies the existence of the phenomenon it cannot explain. It must be noted, however, that human freedom can be the subject of experiments. Actually, every scientific experiment makes use of the freedom of the experimenter.
Since human freedom does not seem compatible with macroscopic determinism or with microscopic indeterminism, let us do what is usually done in science before such a situation: postulate the existence of a new unknown field, open to exploration. This was done, for instance, at the end of the nineteenth century, by Henri Becquerel (1852-1908) when he discovered radioactivity; by Max Planck (1858-1947) with the theory of quanta; by Albert Einstein (1879-1955) with his theory of relativity. Let us postulate that the deep structure of the universe is not a segment with two ends; let us add a dimension and assume that it looks like a triangle with three vertices.
Chaotic determinism, quantum indeterminism and free will could be the three vertices of that triangle, two of them located in the material world (thus subject to the study of science) and the third entering as a spearhead in the supernatural world.
Let us assume that God in his providence can interact with the world through the three vertices of the triangle to drive the development of his intelligent design.
Let us consider a sample case: we believe that the extinction of dinosaurs took place sixty five million years ago as a consequence of the impact of a heavenly body (an asteroid or a comet) against the Earth. After the disappearance of dinosaurs, the mammals, up to then reduced to a small size, found an open field to evolve and invaded all the ecological niches occupied by large animals, which suddenly had become free. This gave rise to the evolutionary chain which led to man. We can imagine that, in an intelligent design leading to the appearance of an intelligent species on Earth, God could have planned that impact in the initial conditions given to the universe at the beginning. Phenomena of this kind happened more than once during the history of Earth and would have made it possible to apply important modifications to the evolutionary process.
Perhaps this mode of action would be appropriate to lead evolution through several critical points spattered through the history of life on Earth, such as photosynthesis, which let life make use of solar energy, freeing it from its dependency on less reliable energy sources, such as lightning or volcanism; or in the transit from one level of life to the next, when several individuals got together, renouncing their individuality, to shape a single organism of the higher level. This has actually happened several dozen times on four different levels.
Fortunately, the third form of divine action is not the only one which God can use to manipulate the universe. Otherwise, we would have an impotent creator, who would depend exclusively on human beings (or any other free intelligent being in the cosmos) to reach his goals, in the style of the gods of the imaginary world described by Lois McMaster Bujold in several novels .
Looking at many things which happen in the world, it seems that God has decided to abstain of acting directly when He can do it through human beings, even though they can fail him. Perhaps, if He did not act so, if He corrected our failures, weaknesses and the negative effects of human egoism and wickedness, He would promote quietism, He would go against our responsibility. Why work, we would say, if God always makes it good? This could be one of the answers to the atheistic argument which says that Auschwitz horrors prove that God does not exist. What they prove, in fact, is that man is responsible, that God is not a machine which automatically corrects all the damages caused by us.
On the other hand, during most of the duration of the cosmos, the third mode of divine action would have been impossible. Only since the origin of man (i.e. the intrusion of the supernatural world in the material universe through our freedom) the second dimension would have entered the structure of the universe, pushing to a triangle the original one-dimensional segment. This is how the biblical statement that the cosmos has been made for human beings should be interpreted. In more modern words, the goal of intelligent design is the rising of beings capable of acting with that freedom, so questioned by atheists and so badly understood by most in the twenty-first century.
During the Middle Ages, as a consequence of Christian cosmology, they believed that man was the center and the reason behind the universe, the most important being in cosmos. Since the sixteenth century, this idea has received blow after blow. First Copernicus took the Earth away from the center. Next Darwin took man away from his special role between living beings, making of him just an animal. Then Freud proved that man is just a mixture of subconscious trends, motivated only by sexuality and fear of death. Finally, during the twentieth century, astronomy has proved that not even the sun or our galaxy play any special role in the cosmos. Therefore man is a totally unimportant being.
This conclusion is an obvious non sequitur. Perhaps because of that, this modern myth has now a practically universal propagation, even in scientific or historic environments, even though it is riddled with falsities, fallacies and half-truths from the beginning to the end. First, even though in the antiquity and the middle ages they believed that the Earth was in the center of the universe, it was not given a special importance because of that. On the contrary, contempt towards Earth and its inhabitants is one of the most common features of the literature of the time. In another paper  I have included a few quotations to prove it.
On the second place, Darwin did not prove (nor apparently had the intention of proving) that man is just an animal. In fact, many present biologists consider the action of the human species on the Earth comparable, even superior, to phenomena such as the origin of life, or the invasion of the continents by green plants, which totally changed the world. Therefore they think that our species should be considered at least a kingdom of nature in the biological classifications.
Man is the only species which, by itself, has changed the aspect of our planet, which has turned (among other things) into an emitter of low frequency electromagnetic radiation; it is the only species in the history of the Earth which by itself uses about 25 percent of all the energy available for living beings; man has accumulated in his brain, his books and his computer memories, more information than all the other living beings together; we are producing a mass extinction affecting almost all the other species; we have eliminated species of living beings consciously and on purpose; finally, we are now able to destroy ourselves. For better or worse, the human species is unique.
The genetic difference between man and its nearest animal relatives (chimps) may be small (perhaps 1.5 percent), but this means nothing. The difference in temperature between water at 99.99 centigrade and water at 100.01 centigrade, at normal pressure at the sea level, is even smaller. However, both forms of water cannot be more different: the first is liquid, the second a gas. Physicists know very well about critical points and state changes. It is evident that, between chimp and man, evolution crossed a critical point which gave rise to a completely new type of being, unique in the history of life on Earth. All the attempts to reduce man to mere animalism are just desperate efforts of ideological atheism to degrade us. At bottom, a means to discredit belief in a creator.
On the other hand, it is also false that Christianity puts man in the center. Just the opposite happens: God is in the center. The role of man in the Christian cosmovision is important, but never central. Oddly enough, it is atheists who insist on putting man in the center, falling thus in a contradiction which perhaps they don't notice, because they seem blind to whatever is outside their preconceived ideas: the opposite attitude to that required by the scientific method. The atheistic strategy degrades man to eliminate God, but once they think they have done it, they try to raise man above everything else, making us the only measure and reason for everything . In fact, some atheists would accept a God, not at the beginning of the universe, but at the end, produced by evolution, by that indefinite progress which has become, in the last two centuries, the most important myth of our age .
The twentieth century, the time of dominance of atheistic ideologies, is also one of the darkest in history: Hitler killed six million Jews, gypsies and other minorities; Stalin, with his purges, thirty million Soviet citizens; Pol Pot and his red Khmers, a third part of the population of Cambodia; day after day, in an unending drip, tens of millions unborn human beings are being massacred. And it is precisely now, with extreme cynicism and pharisaic hypocrisy, when atheists are spreading the idea that religions, specially monotheistic religions, promote violence, adducing examples such as the Spanish inquisition which, in three hundred years, performed three or four thousand executions.
There are fanatics in every field, even in sports fields. But the atheistic fanatics have produced more destruction than the Assyrians, the Huns, the Mongol hordes, and all the peoples which attained along history a sad fame of cruelty and death. Thus it would be ridiculous, if it weren't tragic, that atheists are trying to pose as the most tolerant, the most peaceful, and the only defenders of dialogue and happy human coexistence, when history and the everyday facts prove precisely the opposite.
The three modes of divine action, sketched in this paper, provide an inkling of how God could manipulate an intelligent design of the universe, in such a way that the result may be indistinguishable, from within, from the play of chance. If this is correct, we shall never be able to prove scientifically that the universe is the consequence of an intelligent design (and therefore God's existence). Intelligent design may never become a scientific discipline, if proving its falsity is impossible. However, it is a defensible metaphysical theory, at the same level as denying the existence of a creator and stating that everything in the universe is the consequence of mere chance: an atheistic ideology which is often confused with the theory of evolution, from which it should be clearly distinguished, for the second falls under the umbrella of the scientific method, totally strange to the former.