Michael J Behe. Science, Religion, and Society: An Encyclopedia of History, Culture, and Controversy. Editor: Arri Eisen & Gary Laderman. Volume 2. Armonk, NY: M.E. Sharpe, 2006.
Driving down a road in South Dakota, a foreign visitor to the United States might come upon the odd mountain formation. Even though he had never seen nor heard of Mount Rushmore, it would not cross his mind to imagine that wind, erosion, earthquake, or some other wholly unintelligent process forged the remarkable likenesses to human visages (even if he didn’t recognize them as American presidents). Rather, he would immediately grasp that someone sculpted the faces on the mountain. Somehow he knows that the images were intelligently designed by a conscious agent.
We humans are good at recognizing the effects of intelligence in our world. From fraudulent manipulations of manmade systems (such as lotteries) to purposeful arrangements of pieces of the natural world (such as flowers in a garden), we often conclude with firm certainty that something was not the result of chance alone, that it was constructed or guided or maneuvered by a conscious being. Sometimes we spend a lot of money, effort, and technical expertise to detect the presence of intelligence. For example, in the SETI (Search for Extraterrestrial Intelligence) project, scientists try to detect the existence of intelligent space aliens by scanning the skies for radio signals that may have intentionally or inadvertently been sent to our corner of the universe.
But what if we find the equivalent of Mount Rushmore or an alien radio program in basic parts of nature? What if the fundamental laws of the universe or the foundation of life strike us as designed? Can we then conclude that nature or life was designed by an intelligent agent? Advocates of the design argument contend yes. Critics of the argument say the perception of design in nature is an unreliable intuition.
The History of Intelligent Design
The design argument—that is, the argument that we can know an intelligent being created the world because of the evidence of design in nature—has been debated since antiquity, although it has varied in form and emphasis. The Greek philosopher Aristotle thought the fact that nature seems to work toward a goal—that rocks fall down, that cuts heal, that acorns grow into oaks—is evidence of design, since intelligent agents work toward goals. In his proofs for the existence of God, the medieval philosopher Thomas Aquinas echoed Aristotle, remarking that natural bodies act for a purpose, yet mindless bodies can only act for a purpose if they are directed by an intelligence, as an arrow is directed by an archer. Aquinas went beyond Aristotle in claiming that the source of the directing intelligence was not in nature itself; it was beyond nature in the being we call God.
The most famous version of the design argument is attributed to William Paley, an Anglican clergyman. In Natural Theology, published in the early nineteenth century, Paley contrasted our likely reactions to finding a stone and finding a watch.
In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there, I might possibly answer, that for any thing I knew to the contrary it had lain there forever; nor would it, perhaps, be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place, I should hardly think of the answer which I had before given, that for any thing I knew the watch might have always been there. Yet why should this answer not serve for the watch as well as for the stone; why is it not as admissible in the second case as in the first? For this reason, and for no other, namely, that when we come to inspect the watch, we perceive —what we could not discover in the stone—that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it. . . . This mechanism being observed—it requires indeed an examination of the instrument, and perhaps some previous knowledge of the subject, to perceive and understand it; but being once, as we have said, observed and understood, the inference we think is inevitable, that the watch must have had a maker—that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use.
Paley raises points not previously considered by Aristotle. He notes that our apprehending that the watch had a maker requires an “examination” and understanding of the watch. In other words, we must know what the watch is for and how it works. This implies that our awareness of the design of an object will depend on our state of knowledge about it. Paley also moves beyond Aristotelian “purposes” to consider how separate parts of the watch work together. If the parts of the watch were not fitted to each other, he notes, it would not work. From this, Paley concludes, we know the watch had a designer. In Natural Theology, Paley cites many examples from nature that he thinks are similar to watches in that they have interacting parts, such as mammary glands and hearts.
In the late eighteenth century, some years prior to Paley’s work, the philosopher David Hume criticized the design argument on philosophical grounds. Hume reasoned that likening plants and animals to machines was not a legitimate comparison, since there are so many differences between living and nonliving things that one could not be sure any similarities were due to similar causes. Just because machines required design said nothing about whether animals required design. Hume also contended that, in order to have reason to believe that animals in our world were designed, we would have to have experience of animals being designed in other worlds. Since we have no such experience, we have no basis to conclude animals in our world are designed. Clever as Hume’s reasoning might be, books of design arguments continued to be published, perhaps because the appearance of design in nature was so strong that, in order to supplant it, an alternative, positive explanation for the appearance of design was required. That was given by Darwin.
As a young man, Charles Darwin admired Paley’s Natural Theology. However, Darwin’s voyages on the HMS Beagle and his subsequent thinking eventually led him to a radically different explanation for the appearance of design in nature—the theory of evolution by natural selection. From his observations, Darwin realized that there is variation in all species—not all members of a particular species are identical. From his reading of Thomas Malthus’s work on the geometric growth of populations, Darwin realized that a struggle for existence would result as organisms competed for resources. In such a struggle, if the chance variation of an organism happened to give it any advantage, then on average it would tend to survive and leave offspring. If the offspring inherited the variation, then over time the characteristics of the species would change, as the percentage of the population that had the inherited, advantageous variation increased. With many repetitions of the same scenario, over great periods of time, great changes might occur, until the descendants were hardly recognizable as members of the original species.
Here was a positive explanation for how the appearance of design could arise in nature without the need for an intelligent agent. Over long time periods, by small steps, natural selection honed the shape and structure of biological features until they were so well fitted to their function that they appeared as if they had been made to order. Unlike Hume’s work, Darwin’s positive theory signaled the precipitous decline of the influence of the design argument. It should be noted that none of the biological features that Paley had advanced as examples of design was actually demonstrated to be able to be produced by natural selection. Rather, after Darwin the presumption shifted. Since a plausible general mechanism for producing the appearance of design was available, the design argument lost its force.
The Revitalization of the Design Argument
In the past several decades, the design argument has made a remarkable comeback from its low point in the years after Darwin’s work. The key has been a facet of the argument recognized by William Paley—that the design argument depends on our understanding of nature. Advances in science can drastically affect our evaluation of the strength of the argument, and science has advanced tremendously since the nineteenth century.
The revitalization of the design argument has been led by physics. Progress in physics has shown that many features of the universe must be finely tuned to permit life to exist. One of the first examples of such a feature was noted by the physicist Fred Hoyle, who predicted that the nuclear resonance levels of certain elements would have to occur at very particular frequencies to allow the synthesis of carbon in the nuclear furnaces of stars. Without carbon, life as we know it would be impossible. Hoyle’s prediction was later born out by experiment. Taken aback, Hoyle remarked that it appeared a superintellect had manipulated the laws of physics.
In the mid 1970s, the physicist Brandon Carter coined the term “anthropic principle” to indicate that the universe appears remarkably fine-tuned to allow for life to occur. If any of a number of factors had been different by a small degree, life would not have been possible. Such factors include the value of the charge on the electron, the strength of the fundamental forces of nature, and the rate of expansion of the Big Bang. Some proponents of the design argument contend that the felicity of the many conditions in our universe that permit life are indicative of purposeful design.
The argument for an intelligent designer can be extended from fundamental laws and constants of the universe to finer levels of physical structure. Habitable planets, for example, cannot occur just anywhere throughout a galaxy; many regions of a galaxy are closed off to life because of high fluxes of radiation, frequent supernovas, a paucity of metals, and other factors. Given the physical conditions required, Earth may be uniquely able to support intelligent life. The chemical structure of DNA, the strength of the weaker bonds between biological molecules, and other factors required for life are also finely tuned, suggesting that intelligent design may extend deep into the physical structure of the universe, from the value of the gravitational constant to the chemical properties of the metal molybdenum, which is necessary for incorporating nitrogen into the stream of life.
Some skeptics of the design argument have questioned just how fine-tuned the laws of nature really are. Others speculate about multiple universes coupled to a selection effect. In this view, our universe is only one of very many—perhaps infinitely many—in which the forces and constants of nature can take different values. Since life cannot exist in a universe that does not have the conditions to support it, critics contend it is unsurprising that we find ourselves in a universe compatible with life. Design proponents answer that experimental evidence for an infinite number of universes is lacking, and that speculative, unseen universes are no less metaphysical than an unseen supernatural designer.
The Argument from Biochemistry
Darwin proposed his theory in the nineteenth century, when the molecular basis of life was unknown. The cell then was thought to be a simple structure, essentially a microscopic piece of Jell-O. In the intervening years, and especially in the late twentieth century, science has learned that the cell is exceedingly complex, and that life depends on the existence of intricate molecular machines—quite literally, machines made of molecules—such as the bacterial flagellum, which is a rotary-powered motor that many bacteria use to swim. Our knowledge of biology has greatly advanced since Darwin, which raises the question of whether his theory can wholly account for what has been learned. Proponents of intelligent design argue it cannot.
The argument of design proponents echoes words of Darwin himself who, when discussing the complexity of the eye in On the Origin of Species, remarked: “If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case.” Darwin was emphasizing that his was a gradualistic theory, in which natural selection improved features slowly in small steps over great periods of time. If a complex feature appeared quickly by large leaps, then Darwin thought natural selection acting on random variation would be an unlikely explanation.
In Darwin’s Black Box: The Biochemical Challenge to Evolution, I have argued that a challenge to Darwin’s theory is found in systems that are irreducibly complex. An irreducibly complex system has a number of parts, all of the parts contribute to the function, and the removal of any part causes the system to cease functioning. An example of an irreducibly complex system from everyday life is a mechanical mousetrap. All of the parts of the pictured mousetrap are required for it to work, and if one is removed, it no longer works. Since the function of such a system only appears when it is completely built, their gradual evolutionary construction in small steps by “numerous, successive, slight modifications” is problematic; irreducibly complex systems are difficult to fit into a Darwinian framework.
Yet, many biochemical systems are irreducibly complex, such as the bacterial flagellum. The flagellum is constructed of thirty to forty separate protein parts, the great majority of which are required for it to work. Moreover, the problem of the evolutionary construction of systems like the flagellum is even more difficult than simply manufacturing parts. In our world, intelligent agents physically put together parts of machines, such as mousetraps, to make a functioning whole. In the cell, however, molecular machines have to assemble themselves. To do this, parts of molecular machines must have their surfaces shaped to be exactly complementary to the parts they bind to.
Many see in irreducibly complex systems the hallmarks of intelligent design. Whenever we see complex interactive systems such as a mousetrap, we conclude that the systems were designed. Unexpectedly science has discovered such systems at the molecular foundation of life, and design proponents claim it is a compelling conclusion that those systems too were designed. If this is the case, then intelligent design is not confined to the laws of nature; it extends deep into life itself.
Some critics argue that, although irreducibly complex systems may not evolve directly for their modern function, they may have evolved indirectly by Darwinian processes, with the system changing functions over time and recruiting new parts from other systems. Others remark that experiments already reported in scientific publications show how such systems could arise in small steps. Proponents of intelligent design respond that the significance of the reported experiments is either exaggerated or misconstrued, and that the indirect evolution of irreducibly complex biochemical systems is an exercise in imagination with no experimental support. Some critics of the argument for intelligent design state that science cannot support a theory that invokes the supernatural, since science studies only natural phenomena. Proponents of design answer that the argument does not invoke the supernatural, it invokes intelligence, and that the evidence used to support the conclusion is the data of nature, not mystical revelations.
The intelligent design argument is quite controversial, with the controversy increasing the further into biology design is claimed to extend. Being controversial, however, is a big step up from being forgotten, as the design argument once was. As William Paley knew, the argument’s fortunes depend on our knowledge of nature and, surprisingly to some people, have improved as science has advanced. Since the progress of science continues at breathtaking speed, the coming decades may see a more definitive judgment on the intelligent design argument.