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The battle between secular defenders of evolution and those who believe in a divine Creator is more than a century old. Yet there is no lessening in its emotional and intellectual intensity. The latest wrinkle is Intelligent Design. It is good science, or good theology?
By C. David Grant,
Chair, Religion Department
Just before Christmas of 2005, Judge John E. Jones III of the Middle District Federal Court in Pennsylvania struck down a 2004 Dover Area School Board resolution requiring a statement be read to ninth grade biology classes. That statement, in part, read, "Intelligent Design is an explanation of the origin of life that differs from Darwin's view. The reference book, Of Pandas and People, is available for students who might be interested in gaining an understanding of what Intelligent Design actually involves."
The resolution said neither that intelligent design must be taught alongside Darwin's view of evolution, nor that evolution be excluded from the curriculum. Nonetheless the rejection of this resolution by the Federal Court is significant, for it was the first legal challenge to the promotion of intelligent design in public schools as an alternative scientific explanation for the evolution of life. To understand what is at stake in this ruling, we must look briefly at the history of the idea of intelligent design and its contemporary manifestations. I'll then conclude with the reasons why I, as a Christian theologian, think intelligent design is neither good science nor good theology.
The Historical Background
It seems so obvious: an eye is made for seeing, a hand for grasping, an ear for hearing. The intricate structures of our own bodies and, indeed, of many natural systems seem to cry out for explanation in terms of purpose and design. Ancient Greek philosophers accepted this insight; the medieval Christian theologian and philosopher Thomas Aquinas presents this basic premise as one of his five ways to prove the existence of God. Even Sir Isaac Newton, the father of modern physics who was able to explain all motion - from the path of a thrown ball to the orbits of the planets - under one set of mechanical laws, saw the intricate system of the solar system as only being explained by its having its origin in the mind of a Creator.
Indeed by the early nineteenth century, naturalists and natural philosophers - the word scientist was not invented until well into the 1800s - conjoined their new discoveries about nature with an increasing wonder at the wisdom displayed by the Grand Architect who planned and designed the intricacies of this world then being daily discovered. Indeed a whole series of books was commissioned in England, called the Bridgewater Treatises, in which major naturalists contributed volumes demonstrating "the Power, Wisdom, and Goodness of God, as manifested in the Creation." The idea that the natural world could have no explanation but that of having come about by a creator who designed the world with its many intricacies, was widely accepted by both clergy and naturalists of the day.
William Paley and the Argument from Design
In 1802, this idea of divine design was carefully articulated into a philosophical argument by the Anglican clergyman and naturalist William Paley in his influential Natural Theology. Paley began his argument with a simple illustration: if you came across a watch while walking in a meadow, you would unhesitatingly know that it was the product of an intelligence who make it. When Paley analyzes the characteristics of the watch that lead us to this conclusion, he points to two important features. First, the watch is made up of many complex parts. (Remember, Paley in 1801 was looking at a mechanical pocket watch with gears, springs, casings and the like, not the battery and computer chip found in modern watches!) But second, all those many parts together function for an overall purpose that goes beyond any particular part, the measuring of time. No individual part within the watch can tell time except when conjoined with all the other parts. Yet each individual part is absolutely necessary to the overall purpose. Take away the watch spring and the watch doesn't tell time; take away the hour hand and the watch fails to convey the hour of the day. Since the order of the many watch parts is not inherent in the parts themselves, Paley concludes that the order must be imposed from without by the watch designer who constructs the watch for the particular purpose of telling time. Hence a simple examination of the watch shows that the conjoining of complex parts with an overall purpose can be explained only by a designer. "There cannot be design without a designerc. Arrangement, disposition of parts, subserviency of means to an end, relation of instruments to an use, imply the presence of intelligence and mind."
Having laid the groundwork by discussing the happenstance of finding a watch in a meadow, Paley next turns to the obvious analogy: nature provides us with uncountable instances of just such objects as watches, only more complex and intricate. He examines the eye, pointing out that, just like the watch, it has many parts that individually do not see but in conjunction with all the others have an overall purpose of seeing. The lens, the cornea, the retina, the optic nerve - just like the gears and springs of a watch, these individual components together function for a purpose that transcends any particular part. Hence Paley concludes that the eye, just like the watch, can only be explained by reference to a designer who imposes order on the parts for the sake of the overall purpose. And that designer, concludes Paley, is God. Late eighteenth- and early nineteenth-century British natural philosophy was permeated by a confidence that understanding the natural world would inevitably provide strong support for believing in God.
Charles Darwin's Alternative to Design
A young Cambridge student named Charles Darwin had to read Paley's work for his examinations. He was taken by Paley's argument. Indeed, late in life he says:
"the logic of c [Paley's] 'Natural Theology,' gave me as much delight as did Euclid. The careful study of these works, without attempting to learn any part by rote, was the only part of the academical course which, as I then felt and as I still believe, was of the least use to me in the education of my mind. I did not at that time trouble myself about Paley's premises; and taking these on trust, I was charmed and convinced by the long line of argumentation."
Indeed, part of Darwin's motivation to accept appointment as the naturalist on the H.M.S. Beagle was a desire to find more examples of wonderfully designed creatures to give further evidence of the wisdom of God displayed in nature.
What Darwin found during his years aboard the Beagle from 1836-1839 were indeed marvelous examples of creatures that appeared to be designed explicitly for the environments in which they were found. But on his return, as he reflected on the copious data he had collected, he came to a startlingly different conclusion from Paley's: organic structures that comprise multiple complex parts that function together for a purpose beyond the single parts could evolve through a process of natural selection. Thus a complex structure such as the eye could come about by a long process of very slight changes that, over thousands upon thousands of years, would result in a structure that is very analogous to structures that are brought about by human design over short periods of time.
Darwin presented his theory of descent with modification by means of natural selection in his Origin of Species in 1859. Like Paleyfs insight, Darwin's was based on an analogy. Only his analogy was based not on watches but on animal breeding. Darwin noted that domesticated animals produce offspring with various characteristics. A litter of puppies, for instance will include different size pups, different colorations, different dispositions. Animal breeders then select those pups to raise for further breeding whose characteristics are the ones that the breeder wants to develop in the breed. Selective breeding, or as Darwin terms it, artificial selection, has been very successful in agriculture, resulting in high milk-producing breeds of dairy cows, high egg-producing chickens, and breeds of turkey with high percentages of breast meat.
Darwin's great insight was to apply the same principle of selection to the effects of nature when animals are in a competitive situation. When a particular variation among offspring gives a competitive advantage to an individual in its particular environment, Darwin saw that the natural environment itself functions analogously to a selective breeder. One of the oft cited examples of such a process can be found in the different species of finches in the GalaLpagos Islands. (Interestingly, Darwin himself does not use the GalaLpagos finches as illustrations in The Origin of Species, though he comments on the different finches he found there in his Voyage of the Beagle.) Closely-related species of finches on the GalaLpagos Islands are distinguished by varying beak sizes and types. Finches on islands with ample insects have beaks that are adapted for finding and eating insects; finches on islands with ample vegetation have beaks adapted for eating seeds. What Darwin's theory suggests is that the natural environment acts as a selective breeder in such cases: finch offspring with beak variations that happen to be better suited for breaking seeds will be more successful at surviving, reproducing, and hence passing on the beak variation to succeeding generations of offspring on those islands where seeds are abundant and insects are few, whereas on islands with large insect populations and sparse vegetation, the individuals whose variant beaks are better for rooting out insects are more likely to survive and reproduce. What under Paley's assumptions looked like beaks designed for the particular islands on which species of finch dwelt, on Darwin's assumptions was the result of natural selection operating over long periods of time through many, many generations of offspring. Hence Darwin's alternative explanation of the development of complex structures that function for a purpose that transcends the individual parts quelled the power of Paley's argument from analogy. One could no longer assume that the only explanation for apparent design in nature was an intelligent designer.
By the end of the nineteenth century, Paley's argument from design no longer prevailed in natural philosophy and science as it had earlier in the century. Darwin's convincing case for the evolution of species had reshaped the discussion such that naturalistic explanations for natural phenomena became the focus of twentieth-century science.
Even among religious thinkers, the argument from design was abandoned as a primary tool to convince others of God's existence. Twentieth-century mainline Protestant and Roman Catholic theologians rarely appealed to examples of design in nature to make an argument for the existence of God, although such arguments remained the staple of conservative religious groups. But the argument from design has recently reappeared.
The Rise of "Creation Science"
Its reappearance is due to the efforts of several religiously motivated groups and individuals who see intelligent design as a way of reintroducing religious ideas into science, and hence into the public school arena. Attempts to introduce particular religious views in the public school science classroom have a long history in American education. After the rise of Fundamentalism in the early part of the twentieth century, conservative Christians pushed for laws against the teaching of evolution. One such law in Tennessee was challenged in the 1920s, resulting in the famous trial of John Scopes in which Clarence Darrow and William Jennings Bryan took the respective sides challenging the law and supporting it. Scopes was convicted, though his case was later overturned on a technicality. Nonetheless the Tennessee law against teaching evolution remained in force for decades after the trial. It was not until 1968 in the Supreme Court decision Epperson v. Arkansas that the courts ruled that laws that forbade the teaching of evolution were based on particular religious tenets and hence, based on the First Amendment to the Constitution, were an unconstitutional establishment of a particular religious view as governmentally supported.
After this decision, Christian fundamentalists developed a new strategy to promote their particular religious view in the public schools - the movement known as "creation science" or "scientific creationism." As the courts later described this movement, it was an attempt to have the biblical story of creation taught as science. The leaders of the creation science movement were "young earth creationists": they believed that the earth was but a few thousand years old and that the Creator instantaneously and specially created all the living flora and fauna. Adopting the view known as catastrophism, the "creation scientists" tried to show how the earth's surface and the fossil record were consistent with a massive worldwide flood. Geologists had long ago rejected the views that the earth was but a few thousand years old and the geological record was primarily to be explained as the result of catastrophes, but the scientific creationists suggested that the scientific community was biased against any evidence to the contrary of science's supposed dogmatic, atheistic view of evolution. The scientific creationists made no headway in the scientific community, but they did make headway in fundamentalist Christian groups who organized to influence political decisions. As a result, in spite of its failure to be taken seriously by the scientific community, the creation science movement did gain popular support, and by the early 1980s, two states, Arkansas and Louisiana, passed laws requiring that creation science be taught alongside evolution in the public schools.
As soon as these laws in Arkansas and Louisiana were passed, suits were filed against them by, among others, the leaders of the mainline Christian denominations within these states. The plaintiffs in the Arkansas case included the head of the Presbyterian Church in Arkansas, the United Methodist bishop of Arkansas, and the Roman Catholic and Episcopalian bishops of Arkansas. The mainline religious denominations thus saw the creation science movement for what it was: an attempt by a particular group of Christians to get their particular ideas of creation sanctioned by the state for teaching in public schools. The courts, too, saw that the creation science laws were about the promotion of a particular religious view and declared them unconstitutional on that basis. The Arkansas law was deemed invalid by a U.S. District Court in 1982 and the Louisiana law was struck down by the U.S. Supreme Court in 1987.
The Reappearance of Intelligent Design
As was the case after Epperson v. Arkansas, Christian conservatives were not simply to accept defeat after Edwards v. Aguillard. One such Christian conservative was a professor of law at U.C. Berkeley, Phillip E. Johnson. In 1991 he published Darwin on Trial, a book in which he attacked the standing of Darwinism in the scientific community by subjecting it to the canons of a law court. In that book he advocated that intelligent design is a rational alternative to what he calls the materialistic, anti-theistic conclusions of modern biology. In a later book he openly describes his strategy as driving a wedge into prevailing scientific views so that "Christians, and other believers in God, [can] find common ground in the most fundamental issue - the reality of God as our true Creator."
Though Johnson is considered the father of the contemporary intelligent design movement, two other figures have been its driving force, Michael J. Behe, a biochemist at Lehigh University, and mathematician and philosopher William A. Dembski, currently the Carl F. H. Henry Professor of Science and Theology at Southern Seminary in Louisville. We'll look at each of these figures in turn, but a general comment needs to be made about their approach.
Some critics have attempted to dismiss their views based upon an assumption that intelligent design is just the old creation science in new clothes. But this is not fair to their views. Dembski specifically rejects that intelligent design need imply young earth creationism or a commitment to flood geology. Behe goes further and acknowledges that he holds that the earth is billions of years old and finds the notion that all current species descend from a common ancestor "fairly convincing."
What both Behe and Dembski accept from the earlier creationist movements is the claim that natural explanations are not sufficient to explain natural phenomena: intentional intervention by intelligent agents is the only reasonable conclusion to be drawn from a careful empirical observation of nature. Behe and Dembski, however, come at this issue from different directions.
Behe's approach is a molecular version of Paley's analysis of an eye. Behe looks at different examples of biochemical systems - the cilium of cells, the bacterial flagellum, and the clotting mechanism of the blood, to name a few. What he argues is that the complexity of these intricate systems simply cannot be explained on naturalist assumptions but demands involvement by an intelligent designer. Let's look at his argument in some detail.
Behe first asks us to question a fundamental tenet of Darwin's view - that complex organic structures can evolve over long periods of time by very small gradual changes brought about by natural selection operating on what we now call mutations. Darwin's view assumes the human eye evolved from simpler eyes, and simpler eyes evolved from light-sensitive cells in ancient evolutionary ancestors. This process would have occurred over millions and millions of years of natural selection. Behe questions how a complex structure with many, many parts could conceivably evolve from precursors with far fewer parts. For Behe, one can understand how selection works on improving parts of a complex structure once one has the parts, but his question is how additional parts arise in the first place.
Behe's central illustration to explain his point is a mousetrap: a mousetrap is made up of a base, a hammer, a spring that propels the hammer, a catch, and a holding bar. A mousetrap exhibits a characteristic that Behe calls irreducible complexity: if one takes away any one of the parts, the mousetrap no longer functions. Thus, a mousetrap without a catch can't catch a mouse, nor can one without a spring, Behe says that Darwinian evolution assumes that natural selection operates to improve existing adaptations, but how could one get the our parts of the mousetrap in the first place, since without them all being present in the mousetrap they individually have no function?
Just as Paley compares an eye with a pocket watch, so Behe compares a mousetrap with a bacterial flagellum. A flagellum is a hair-like structure that bacteria use for moving. It is rooted to a kind of molecular motor that spins the flagellum like a corkscrew, thus propelling it. As a biochemist, Behe is in a good position to take his readers though a description of a bacterial flagellum, a very simple molecular structure. The flagellum comprises at least forty different proteins - the analogy to the "parts" of the mousetrap - each of which appears to have a specific function in the flagellum and its molecular motor. He asks the question, How could these forty proteins, the function of each being dependent on the total structure of the flagellum, have evolved along Darwinian lines? He points out that biologists have no descriptions of evolutionary pathways for these proteins. They are irreducibly complex. That is, we can't explain how they might have evolved on Darwinian lines, so Behe opts for an alternative: the evolutionary pathways were directed by an intelligence that foresaw the final product and drove evolution along the appropriate pathways to achieve the desired end. Some intelligence - whether that be God on some other being - is the reasonable explanation for the irreducible complexity of our living world.
A couple of things need to be said as we begin to evaluate Behe's views. First, Behe has not received much support from his fellow scientists for his arguments favoring intelligent design as a scientific explanation of irreducibly complex molecular structures. Indeed, his own faculty colleagues in the Department of Biological Sciences at Lehigh University have explicitly rejected his view:
While we respect Prof. Behe's right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally, and should not be regarded as scientific.
Second, this is not the case of atheist scientists attacking a person who holds religious views. Indeed, many of Behe's staunchest critics are themselves religious believers, including Kenneth R. Miller, to whom we'll refer below. It is a question about the scientific merits of a proposed scientific view, and that, according to many of Behe's critics, is where his resuscitation of the argument from design falls short.
Kenneth R. Miller, cell biologist at Brown University, points out that Behe's premise of eirreducible complexity" is fundamentally flawed, because it assumes that one can only look at the function of parts of a system in that completed system. But evolutionary pathways certainly do not have to be so narrowly defined. For instance, take the mousetrap example. Behe's points out that a mousetrap without the holding bar is useless as a mousetrap. True, enough. But Miller points out that it is still perfectly functional as a tie clip or paper clip. The base can function as a paperweight and the holding bar can itself be fashioned into a fishhook. Likewise, in the bacterial flagellum, some of its proteins have another function in other bacteria. For instance, a small group of these proteins are used "as a device for injecting poisons into other cells." It is true that the evolutionary pathways of many of the proteins in the bacterial flagellum may be unknown to science at this point. But simply to rule out the possibility that such natural pathways exist yet to be discovered is simply to run counter to the methods employed by natural science.
This same problem operates in the arguments of the other leading exponent of intelligent design today, William A. Dembski. Dembski is trained as a mathematician and philosopher. His work centers on the logic of the argument from design more than the content of the argument. The basis of Dembski's proposal is what he calls his explanatory filter. Our explanations of events and structures proceed through a logical pattern in basically three steps. Those three steps are necessity, chance, and design. He states that as we try to determine the source of a phenomenon, we first ask if it is a product of law. For instance, to explain the rising of the tides, we simply need to refer to the relevant laws of gravitation long ago developed by Sir Isaac Newton. If it is a product of natural law, then we've explained the event by the necessity of natural law. But some events cannot be fully explained by natural law. For such events chance plays a role. For instance, to explain why the oak tree sapling sprouted at the particular place in my garden that it did requires more than natural law. It depends on chance events - where the acorn happened to grow on my oak tree, how the acorn fell from the tree, how the acorn bounced when it struck the ground, and whether a squirrel happened to find the acorn and where the squirrel happened to bury it. The odds of the acorn ending up at that particular place in my garden are small and hence a direct appeal to the regularities of nature does not sufficiently explain its final sprouting place.
What Dembski says next is that if an event in question cannot be explained by chance and it cannot be explained by necessity, then it must be explained by design. That is, his explanatory filter defaults to design as the explanation when the other two explanations are found wanting. This amounts to an exclusive disjunctive argument that philosophers put in the form: either p or q or r. Something must be one of these three options, and it cannot be more than one. Let's illustrate this exclusive disjunction this way. We'll start with a premise: I have one current U.S. coin in my pocket worth less than 25. That means that it is either a penny or a nickel or a dime. If I give you two guesses, you'll know what coin it is, even if you don't guess the right coin. Say I have a dime in my pocket and your first guess is that it is a nickel. I tell you you're wrong. Then you guess, a penny. I again tell you you're wrong, but because the three choices are an exclusive disjunction, you now know that the coin is a dime even though you've not even mentioned it.
Dembski's filter is a similar exclusive disjunction, but it is an ordered disjunction: one must eliminate the possibilities in an ordered sequence. First one must eliminate necessity, and second, chance. But like my coin example, one doesn't have to show that something is designed; one only has to show that the event or phenomenon can't be explained by either necessity or chance. If one can show this, then Dembski's filter defaults to design. In such a scheme, the default member of the disjunction is given a privileged status by simply the way the argument is set up.
Design has to do with intention. We have many examples in our common experience of intentional actions of agents trying to bring out an end that would not, in the normal course of nature, come about. The popularity of shows dealing with forensic criminology - the C.S.I series in its Las Vegas, Miami, and New York incarnations, for example - gives us an example to explore. Let's say a man is found dead with no apparent signs of physical trauma. How do we go about determining whether the person was murdered (his death was brought about by design - another individual intended his death) or died of natural causes? I believe that normally we first look for evidence of criminal activity; if none is evident, then attention switches to seeking natural causes. Let's say we determine that the subject died of a heart arrhythmia. Was it the result of intentional electrocution or injection by drugs, or was it simply a result of natural causes which ultimately include chance factors? Tests are run to eliminate the presence of drugs; the body is carefully examined to find telltale signs of electrocution. In the absence of these findings, the default explanation is that the person died of natural causes and was not murdered. Science proceeds, that is to say, on the assumption that events can be explained through natural means unless there is evidence to suggest intentional intervention. Dembski's filter, in my mind, loads the case ahead of time by placing design as the default explanation that remains after necessity and chance have been eliminated. But I'm not sure that it conveys the sort of reasoning process that we use in science, much less in everyday life, concerning events in the world around us.
Concluding Theological Comments
But as a Christian theologian, I have an even greater concern with intelligent design than these issues. For the view seems to imply certain things about God that many who consider themselves Christian believers find problematic. Let's start with the disjunctive character of Dembski's explanatory filter. Remember, the filter works by the three categories of necessity, chance, and design being exclusive alternatives. Hence if one determines that something is the result of natural law, then Dembski's filter precludes one's talking about that as being of God's intention or design. But throughout the history of Christian theology, the doctrines of creation and providence posit that God can operate in the world through natural law and chance occurrences. Indeed, attributing divine intention only to those things that cannot be explained by natural law and chance relegates God's activity in the world to what are occasional interventions in our world of experience. Likewise Behe's designer comes to play only in those instances in which we have irreducible complexity. When things are explainable on the basis of science there's no need to invoke God as a cause among causes.
Which is another problem I have with the intelligent design approach. Traditional theology has always held that God's causality in the world operates at an entirely different level than worldly causes. Traditionally this distinction is made by describing God as the primary cause of all that happens even though we can also explain things that happen through secondary causes. Secondary causes are the sorts of causes we study in science, what Aristotle called efficient causes. These primary and secondary causes operate at two different levels; one is not an alternative explanation to the other.
Perhaps an analogy here will help. I've just pressed the shift key and the i key on my computer keyboard to type the letter that begins this sentence. Now we could describe that keystroke in a number of ways: were we studying kinesiology, we could talk about the various muscle groups that contracted in the particular fingers that moved. We could describe the nerve pathways that carried the signal to the various muscle fibers. We could talk about the tendons and bones on which the muscles are anchored and the joints that pivot as the muscles contract. What caused the keys to move? Certainly this complex set of physiological muscle events.
But could another explanation be that I typed a capital I? Of course. In fact, we are more likely to describe the event in this way than as the result of the physiology of the finger. Well, then, which is the correct explanation? I hope you're thinking, "Well that's an odd question," for we know that both explanations are correct. They are not alternative explanations, disjunctive explanations in the sense that if one is right the other is wrong. They are different levels of explanation of the phenomenon we're describing.
The claim that God created the world and all that is within it is a religious claim, not a scientific claim. As many thoughtful scientists and religious believers have held for decades, one can believe in God and accept the findings of science. Intelligent design brings God down to being one force operating in nature among other forces. It implies that nature goes along on its own laws until an intervention from God tweaks a mutation here or an environment there to bring about a divine intention, intervening in the natural process to bring about something that otherwise would not be.
The traditional notion of God in Christian faith is as the sovereign power that creates, undergirds, and sustains the entire cosmos. God is no tweaker, no force among forces, no partial explanation for the particularities of unexplained natural phenomena.
If intelligent design fails as an alternative scientific explanation to natural selection, then it doubly fails to render a fully adequate notion of God and God's presence and activity in creation. As compelling as it may be to desire God to be a factor in our scientific explanations, we do greater religious service to God by studying nature on its own terms and worshipping God as the ever-present creator and sustainer of all creation and not just as an occasional tweaker of an otherwise self-sufficient natural world.
C. David Grant is Professor of Religion at TCU. A popular and award-winning teacher, he has been at TCU since 1981 and currently serves as chair of the Religion Department. He directed the TCU Honors Program from 1988-1994 and is the author of three books: God the Center of Value (1984), Thinking Through Our Faith (1998), and A Theology of God's Grace (2004). He is currently working on a project exploring the relationship between evolution and Christian faith.
Thanks to Professors Phil Hartman and John Horner in Biology and Professor Nadia Lahutsky in Religion for reading and commenting on this essay.
Contact Grant at firstname.lastname@example.org
The Intelligent Design and Evolution Awareness (IDEA) Center:
National Center for Science Education:
The Discovery Institute:
Pennsylvania's ACLU on the Dover trial: www.aclupa.org/education/intelligentdesignchallenge.htm
Institute for Creation Research: