How Intelligent Design Works

A close up of a woman using her intelligent home system to control appliances in the house.
Intelligent design states that the universe and its inhabitants could not have evolved by blind chance. d3sign / Getty Images

Not so long ago, there were two major competing theories in the United States regarding the origins of life: evolution and creationism. Evolution represented science's opinion of how the universe began, and creationism offered the religious explanation. It was pretty cut and dry. Then came "intelligent design."



­The intelligent design (ID) movement claims that life as we know it could not have developed through random natural processes -- that only the guidance of an intelligent power can explain the complexity and diversity that we see today.

How does intelligent design explain the origins of life? Does it fit the criteria of a scientific theory, or is it religious dogma in a scientific wrapper? In this article, we'll examine intelligent design and the controversy it has generated.


What is Intelligent Design?

Intelligent design (ID) states that the universe and its inhabitants could not have evolved by the "blind chance" set forth in Darwinism. Its arguments are mostly concerned with what it considers to be holes in the theory of evolution, and it claims that these holes scientifically prove the presence of an "intelligent designer" in nature.

Unlike creationism, ID does not state that God is the intelligent designer. It only says that there is clear evidence in nature of intelligent design. The designer in ID could be God, but it could also be an extraterrestrial race or some other supernatural force. Also, ID does not draw its arguments directly from the Christian Bible.


But while it does acknowledge the possibility of slight evolutionary changes within a species, it does not recognize the possibility of one species evolving from another nor the chance of highly complex biological systems resulting from natural selection. ID proponents have stated that they aim to debunk Darwinism as the dominant origin theory and to remove naturalism -- the belief that everything around us can be explained by natural causes -- from both science and culture.

The Science of Intelligent Design

While the intelligent design movement has, at present, made more of a mark on politics than on science, it nonetheless defines itself as a scientific movement and sets forth various arguments to support that claim. The science of intelligent design is very controversial -- the scientific community does not recognize its methods as scientific -- and its arguments do not always form a cohesive vision of the scientific evidence for design. Instead, this evidence consists of the work of several scientists all setting forth their own theories in support of an intelligent, supernatural designer at work in nature. The common thread in the science of ID lies mostly in the structure of the work, all of which adheres to a double goal: To disprove Darwinism and to prove design in nature.

Some intelligent design arguments apply to both goals, and most of them are interconnected; but in the interest of structure, we will group them here according to which aim they most directly address. In the following sections, we'll examine the more prominent intelligent design claims, including:


  • To disprove Darwinism: Irreducible complexity; Specified complexity; Law of Conservation of Information
  • To prove design: Three-stage "Explanatory Filter"

ID Goal: To Disprove Darwinism

Irreducibly complex?
Photo courtesy HSW Shopper

Michael Behe: Irreducible complexity

Irreducible complexity essentially states that there are biological structures that could not have evolved from a simpler state. A cell, for example, is composed of hundreds of complex molecular machines. Without any one of those machines, the cell would not work. So the cell is irreducibly complex: It couldn't have evolved from a simpler state because it couldn't have worked in a simpler state, and natural selection can only choose among traits that are already functioning.

Behe offers the example of a mousetrap, which typically has five parts: a wooden base to support the contraption, a metal hammer to pound the mouse, a spring to power the hammer, a catch to release the spring and a metal bar that holds back the hammer. Without any one of these parts, the device is useless. Therefore, a mouse trap is irreducibly complex.


In biology, Behe sees the bacterial flagellum as an irreducibly complex system.

A flagellum works as a propeller to help some bacteria get around. This "propeller" contains about 30 different proteins that make it work -- some act as a motor, some act as a stator and others act as a bushing to guide the driveshaft through the bacterial membrane. Without almost any one of these 30 proteins, the entire system breaks down [ref].

The scientific community responds to irreducible complexity by stating that while it is true that natural selection can only choose among traits that are already functioning, the traits don't have to be functioning in their current form. They could have been serving other purposes when they were chosen as advantageous for their current function.

In the example of the mouse trap, scientists point out that if you remove the catch and metal bar, you've got a tie clip. If you remove the spring, you've got a nice keychain. They also claim that science has already discovered that a group of the proteins that make up bacterial flagella is used by certain bacteria for an entirely different function: It acts as a sort of "molecular pump" in the bacterial membrane.

Biologist Kenneth Miller states, "The point, which science has long understood, is that bits and pieces of supposedly irreducibly complex machines may have different -- but still useful -- functions ... Evolution produces complex biochemical machines by copying, modifying, and combining proteins previously used for other functions" [ref].

William Dembski: Specified complexity

Specified complexity in a system means it could not have occurred by chance and it is not the result of any natural law that says it must be the way it is. A biological system exhibits specified complexity if it meets three criteria:

  • Its makeup is not merely the result of a natural law.
  • Its makeup is complex.
  • Its makeup reflects an "independently given pattern or specification."

For clarification, Dembski refers us to the example of detecting an extraterrestrial radio signal in the movie "Contact."

The radio astronomers in "Contact" detected design in a radio signal when they discovered its pulses reflected all and only the prime numbers from 2 to 101. It was not the result of necessity -- there is no law that requires radio signals to transmit in that pattern; it was complex -- the series of signals was long and so was unlikely to take that particular form by chance; and the series of signals reflected an objective pattern -- one that was specified in mathematics long before the astronomers received the radio signal. This signal had specified complexity, and Ellie Arroway and crew took this as evidence of intelligent design.

According to Dembski, a biological system is clearly designed if it exhibits specified complexity.

The scientific community sees this argument as inherently flawed. It points out that Dembski sets forth a negative hypothesis: Anything not created by chance or law must be designed. But scientists claim that chance, law and design are not mutually exclusive, and they are not the only possibilities. So the process of elimination cannot be applied. And in any event, they say, science does not accept the process of elimination as proof of anything. The scientific method requires a positive hypotheses -- you cannot prove one thing simply by disproving another.

Another objection to Dembski's method of detecting design is that it appears to necessitate prior knowledge of the specified pattern. If the radio astronomers in "Contact" had no knowledge of the natural laws governing radio signals and did not recognize consecutive prime numbers as a mathematical sequence, they would never have detected a pattern. When dealing with something like DNA, scientists claim, there are no externally recognizable patterns and therefore no way to detect if a pattern occurs by chance or was "independently given." Dembski's process of detecting design presupposes design [ref].

William Dembski: Law of Conservation of Information

The Law of Conservation of Information was created by William Dembski and involves some very detailed and complex mathematical equations. At its most basic, Dembski's law states that nature cannot create new information (as in information contained in DNA); it can only work with the information it already has. Therefore, a more complex species -- one that contains more information -- could not have evolved from a less complex species [ref].

The scientific community believes that Dembski is repackaging the creationist argument that the theory of evolution violates the second law of thermodynamics, which states that there is a tendency in nature for complexity to decrease. It claims that science has understood for a long time that this theory applies "only to closed systems, and biological systems are not closed" [ref].


ID Goal: To Prove Design

William Dembski has come up with what he considers a fool-proof method of detecting design. This method is a process of elimination that asks three questions of anything found in nature:

  1. Does a law explain it?
  2. Does chance explain it?
  3. Does design explain it?

This is similar to the process of detecting specified complexity. To explain the filtering process in common language, Dembski uses the example of a 1985 civil case tried in the New Jersey Supreme Court. The case involved county clerk Nicholas Caputo, who was accused by the Republican party of rigging elections by always putting the name of the Democratic candidate at the top of the ballot. According to Dembski, this is known to increase a candidate's chances of winning. Dembski asserts that the court must have considered the three options in his Explanatory Filter in order to determine whether Caputo had intentionally placed Democrats in the first position on the ballots.


First, the court had to determine whether the placement occurred by law. That is, did Caputo unknowingly subject the process to a law of odds that explains the coincidence? Did he believe he was using a truly random method to determine placement when in fact the method was flawed and was sure to result with the Democratic name in position one? If the answer was no, the court would move to question two and ask whether Caputo's method was in fact random. Was it by pure chance that the democratic candidate always ended up on position one? If the court discovered a pattern -- i.e. the first position on the ballot was always occupied by the candidate from a single political party -- then it could not be the result of chance. So, if Caputo's method was not truly random, and it was already determined that it was not the result of a law that kicked in because of a mistakenly flawed method, then it must be the result of design. In other words, the only option left is that Caputo knew he was cheating: The Democratic name always ended up at the top of the ballot by design.

Dembski explains that we actually use this method all the time, probably without even knowing it. It is only a matter of quantifying the process in order to make it scientific instead of merely instinctive. In its quantitative form -- the Explanatory Filter -- it can be applied to scientific questions as successfully as it is applied to questions that arise in everyday life.

Using this method, Dembski argues, will never result in a false positive for design. However, he notes that there could be a problem of false negatives:

One difficulty is that intelligent causes can mimic law and chance, thereby rendering their actions indistinguishable from these unintelligent causes. It takes an intelligent cause to know an intelligent cause, but if we don't know enough, we'll miss it [ref].

The response by the scientific community to Dembski's three-pronged approach to identifying design is essentially the same as its response to his argument for specified complexity. Most scientists note that it is not, in fact, a positive test for design, but in fact a negative test for eliminating chance and necessity. The process of elimination can not lead to any definitive conclusion in the world of science.

Overall, the most significant objection by the scientific community to intelligent design as a scientific theory is that it not empirical. Scientists cannot test for the presence of design, nor can they disprove the presence of design. By its very nature, scientists claim, intelligent design is not a scientific argument but a philosophical one.


Controversy: Creationism in Disguise?

Michelangelo's "Creation of Adam"

The intelligent design movement has created quite a stir in the United States. ID proponents claim that their theory is scientifically sound and is not based on any religious beliefs, and it should be taught alongside evolution in public-school science classes. The scientific community claims that intelligent design is not scientific at all and is in fact a metaphysical theory that should be taught in philosophy class, not science class.

People who object to the inclusion of intelligent design in science instruction are concerned not only about what the scientific community considers to be bad science, but also about what the leaders of the ID movement have said to their followers. A mission statement of the Discovery Institute's Center for Science and Culture (then the Center for the Renewal of Science and Culture) states:


Discovery Institute's Center for the Renewal of Science and Culture seeks nothing less than the overthrow of materialism and its cultural legacies. Bringing together leading scholars from the natural sciences and those from the humanities and social sciences, the Center explores how new developments in biology, physics and cognitive science raise serious doubts about scientific materialism and have re-opened the case for a broadly theistic understanding of nature [ref].

At the same time, statements from ID movement leaders call greatly on religion. Phillip E. Johnson of the Discovery Institute, speaking of the purpose of the ID movement, has said:

The objective ... is to convince people that Darwinism is inherently atheistic, thus shifting the debate from creationism vs. evolution to the existence of God vs. the non-existence of God [ref].

In the July/August, 1999, issue of Touchstone Magazine, William Dembski says, "... intelligent design is just the Logos theology of John's Gospel restated in the idiom of information theory." And later, in 2005, he makes the following remarks:

... intelligent design should be understood as the evidence that God has placed in nature to show that the physical world is the product of intelligence and not simply the result of mindless material forces. This evidence is available to all apart from the special revelation of God in salvation history as recounted in Scripture.

... To be sure, creationists who support intelligent design think it does not go far enough in elucidating the Christian understanding of creation. And they are right!

... Even so, there is an immediate payoff to intelligent design: it destroys the atheistic legacy of Darwinian evolution. Intelligent design makes it impossible to be an intellectually fulfilled atheist. This gives intelligent design incredible traction as a tool for apologetics, opening up the God-question to individuals who think that science has buried God [ref].

There are also widespread claims that the majority of the Discovery Institute's funding comes from Christian fundamentalist organizations and individuals, noting especially the millions of dollars donated by philanthropist Howard Ahmanson, an evangelical Christian, and hundreds of thousands of dollars provided by the Maclellan Foundation, which seeks to "serve strategic international and national organizations committed to furthering the Kingdom of Christ ... by providing financial and leadership resources to extend the Kingdom of God to every tribe, nation, people, and tongue" [ref]. The Discovery Institute responds by saying that the avenues of its research are determined by its board of directors, not its financial supporters.

All of this, along with questions as to the scientific validity of intelligent design arguments, has led many to believe that the intelligent design movement is a calculated approach to get a creationist view of the origins of life into public-school science classes -- that it is in fact religion disguised as science. Proponents of ID insist that this is not the case -- that intelligent design is separate from creationism and is based entirely on scientific evidence.


Origins and Progress of the ID Movement

Photo courtesy Morguefile

In the 18th and 19th centuries and until the introduction of Darwin's theory of evolution, the "argument from design" was the prevailing view of the origins of the natural world.

In 1802, this view was crystallized in William Paley's watchmaker analogy. It goes something like this: If you find a watch in the middle of a field, you note that it is a complex object that serves a particular purpose. It has many different parts that all work together to tell time. When you see the watch, you automatically understand it is the product of design, not chance. It follows that we should assume the same of natural world when it displays complex processes that meet a particular need.


The argument from design reigned until Darwin published "The Origin of Species" in 1859. Biological science responded overwhelmingly to Darwin's evidence and quickly adopted evolution as the prevailing explanation of the development of the universe and life. And by 1940, almost all the biologists in the world believed that natural selection was driving force behind evolution.

Then, in 1991, law professor Phillip E. Johnson effectively launched the intelligent-design movement with his best-selling book, "Darwin on Trial." The movement quickly gained momentum in the United States. In 1996, the Discovery Institute, a think tank based in Seattle, launched the Center for the Renewal of Science and Culture (CRSC). The CRSC's original mission statement included studying and promoting intelligent design as a scientific theory.

Politically, the ID movement has made incredible strides in a short amount of time. In 1999, just eight years after the movement really took off, the Kansas Board of Education voted to remove evolution from Kansas schools' science curriculum, and the decision was widely attributed to campaigning by proponents of intelligent design. In 2004, the Dover Area School Board in Pennsylvania decided to require that all public schools in the district teach ID alongside evolution in science classes. A year later, a U.S. District Court Judge ruled that the requirement was unconstitutional.

For more information on intelligent design, creation, evolution and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links


  • Dembski, William A., Ph.D. "The Explanatory Filter: A three-part filter for understanding how to separate and identify cause from intelligent design."
  • Dembski, William A., Ph.D. "The Intelligent Design Movement."
  • "Intelligent Design?" Natural History, April 2002.
  • The Maclellan Foundation.
  • Miller, Kenneth R. "Darwin's Pope?" Harvard Divinity Bulletin.
  • Orr, Allen H. "Master Planned." The New Yorker, May 30, 2005.
  • "Politicized Scholars Put Evolution on the Defensive." The New York Times, August 21, 2005.
  • The Skeptic's Dictionary: Intelligent Design.