Suppose you are out on a walk and you see a stick leaning against a tree. Is this an evidence of intelligent activity? Not necessarily. Branches often break from trees, and sometimes when they fall, they end up leaning against trees.
But suppose you find three sticks leaning against each other in such a way that removal of any one stick would cause the other two to fall to the ground. In other words, all three sticks must have come together simultaneously. The probability of such an event just happening is extremely low. Most people would conclude that someone must have arranged the sticks to make that tripod.
Two features suggest intelligent design in the tripod: complexity and functional interdependence. The tripod is complex because it has three parts. It is functionally interdependent because removing any one of the parts would destroy the tripod. A structure that is composed of three or more parts, all of which must come into relationship simultaneously, is best interpreted as being the product of intelligent design. Although one can always argue that such a structure could have originated by chance, most people would find such an interpretation hard to believe.
Can such an argument be reasonably extended to nature? If so, do we see evidence in nature of intelligent design?
The argument from design
The Scriptures affirm that God can be seen in nature: “His invisible attributes, that is to say his everlasting power and deity, have been visible, ever since the world began, to the eye of reason, in the things he has made” (Romans 1:20, NEB).* And for centuries, the idea that nature was the product of the intelligent design of the Creator the Bible depicts was accepted without question or controversy. William Paley made such an argument.
Paley and the argument from contrivance. Paley claimed that nature is full of features that show evidence of design. He called them “contrivances” and compared them to human-made devices or machines.
Paley’s most famous illustration involved a watch. Suppose you found a watch, having never seen one before, he said. Wouldn’t you recognize that someone had designed and made the watch for a purpose, even if you didn’t understand the purpose? Similarly, many parts of living organisms function like machines. If we allow that mechanical devices give evidence of a designer, we should also recognize the evidence for a Designer when we see similar features in living organisms. According to Paley, the properties of design evident in nature point to a Divine Designer.
Charles Darwin and the argument against design. Charles Darwin, however, could not accept Paley’s argument. He said that though he found the argument charming, he could not blame God for designing all the evil in nature. He suggested that God was so far removed from nature that He was not responsible for the state of nature and that nature did not point to a Designer. Darwin proposed that instead of God, it was simply the process of natural selection that originated the adaptive features we see in living organisms.
Was Darwin’s argument valid? Darwin himself identified what would disprove his theory. In chapter 6 of his book On the Origin of Species, he stated, “If it could be demonstrated that any complex organ existed [that] could not possibly have been formed by numerous successive, slight modifications, my theory would absolutely break down.”
Darwin claimed he could find no such cases. Others say they have.
Arguments for design
So far we’ve said that some people base their belief that God created our world on the evidence that it was designed by some intelligent Being. The strength of this argument depends on the strength of the evidence for design in nature. Let’s look at two examples of this evidence.
An argument from “irreducible complexity.” Michael Behe of Lehigh University in Pennsylvania is one of the current leaders of the argument for design. He bases his argument on what he calls “irreducible complexity.” For an illustration, he points to the mousetrap. The parts of the mousetrap work together to perform a function—catching mice. If any one of the components of the mousetrap is removed, the mousetrap will not work. So, the mousetrap is an irreducibly complex mechanism. If any such mechanisms could be found in living organisms, Darwin’s theory would “absolutely break down.” According to Behe, cilia are just such mechanisms.
A cilium is a small hair-like structure that sweeps back and forth. The one-celled organisms that have cilia use them to swim. Cilia are also present in our respiratory tracts. Their movements sweep foreign particles from our lungs.
Cilia require at least three parts for active movement: a part that moves, an energy supply, and an “anchor” to control the position of the movable part. Molecules of tubulin make up a cilium’s moving part, the activities of molecules of dynein supply the energy for its movement, and molecules of nexin hold its parts together. Without any one of these, the cilium couldn’t function. So cilia appear to be irreducibly complex.
As one might expect, those who are philosophically committed to evolution refuse to accept the argument from irreducible complexity. However, their rejection is based on philosophical grounds rather than on evidence from nature—as revealed by the total lack of demonstration of evolutionary claims.
An argument from improbability. Some circumstances seem so unexpected that one suspects there must be something more than chance involved. Most scientists are willing to attribute a result to chance if it could be expected to occur by chance as often as five times in 100 trials. Some scientists will lower the acceptable odds to one chance in 1,000 trials, depending on the nature of the event. But there are limits to what anyone will reasonably accept as the result of chance. If the probability of an event is exceedingly low, it is reasonable to suppose that it did not happen as the result of chance. If the event also seems to have a purpose, it is reasonable to suppose that the event was guided by an intelligent mind.
Darwin admitted that he “shuddered” when he thought of the problem of the evolution of the human eye. He tried to make a case for the evolution of the eye by pointing to a variety of less complex eyes in other animals and suggesting that they might represent stages from which a more complex eye evolved. However, it is not clear that he convinced even himself. The evolution of the eye would require an elaborate series of improbable events that most people would consider unlikely to occur without a designer.
The argument for design was widely ignored in the century after Darwin, in part because scientists knew so little about living systems that they could use their imaginations to fill the gaps in their theory of evolution. However, the increase of biological knowledge has revived the argument for design. The existence of certain features that could not survive in intermediate stages and so would not likely be the result of chance provide good evidence of a Designer who created by special creation and not through a continuous process such as evolution.