5 Flawed Arguments for Intelligent Design

Human Evolution
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Intelligent design is the belief that life is too complicated to have arisen solely by Darwinian natural selection and was purposefully created—not necessarily by God (though this is what most intelligent design advocates believe), but by an unspecified, super-advanced intelligence. People who believe in intelligent design often advance some variant of five basic arguments; in the following slides, we describe these arguments and show why they make no sense from a scientific perspective (or why the phenomena they purport to explain are actually better explained by Darwinian evolution).

"The Watchmaker"

The argument: Over 200 years ago, the British theologian William Paley presented a seemingly irrefutable case in favor of God's creation of the world: if, Paley said, he happened to be out walking, and discovered a watch buried in the ground, he would have no choice but to invoke "an artificer, or artificers, who formed the watch for the purpose which we find it actually to answer; who comprehended its construction, and designed its use." This has been the battle cry of intelligent design advocates, and disbelievers in the theory of evolution, ever since Charles Darwin published On The Origin of Species in 1852: how could the intricate perfection of living organisms possibly have come about except by the will of a supernatural entity?

​Why it's flawed: There are two ways to counter the Watchmaker argument, one serious and scientific, the other amusing and frivolous. Seriously and scientifically, Darwinian evolution by mutation and natural selection (Richard Dawkins' "Blind Watchmaker") does a much better job of explaining the supposed perfection of living organisms than the mysterious invocation of God or an intelligent designer. (The first position is supported by empirical evidence; the latter only by faith and wishful thinking.) Amusingly and frivolously, there are plenty of features in the living world that are anything but "perfect," and could only have been designed by an entity that wasn't getting enough sleep. A good example is Rubisco, the enormous, slow, and extremely inefficient protein that plants use to suck the carbon out of carbon dioxide.

"Irreducible Complexity"

The argument: At the sub-microscopic level, biochemical systems are extremely complex, relying on elaborate interactions and feedback loops between organic enzymes, molecules of water and carbon dioxide, and the energy provided by sunlight or thermal vents. If, for example, you remove even one component of a ribosome (the giant molecule that converts the genetic information contained in DNA into the instructions to build proteins), the entire structure ceases to function. Clearly, intelligent design advocates say, such a system could not have evolved gradually, by Darwinian means, since it is "irreducibly complex" and therefore must have been created in toto as a functioning whole.

Why it's flawed: The "irreducible complexity" argument makes two basic mistakes. First, it assumes that evolution is always a linear process; it's possible that the first primordial ribosome only began functioning when a random molecular component was removed, rather than added (which is an extremely improbable event in itself, but one with a high probability over hundreds of millions of years of trial and error). Second, it's often the case that the components of a biological system evolve for one reason (or for no reason at all), and then are later "exapted" for another purpose. A (previously useless) protein in a complex biological system may "discover" its true function only when another protein is randomly added—which eliminates the need for an Intelligent Designer.

Cosmological Fine-Tuning

The argument: Life has appeared in at least one place in the universe—the earth—which means that the laws of nature must be friendly to the creation of life. As far as it goes, this is a complete tautology; clearly, you wouldn't be reading this article if our universe didn't allow life to evolve! However, intelligent design advocates take this "anthropic principle" one step further, claiming that the fine-tuning of the laws of the universe can only be explained by the existence of a grand Designer, and could not possibly have come about by any natural physical process. (One interesting facet of this argument is that it's entirely consistent with Darwinian evolution; the "intelligent design" part of the equation has simply been pushed back to the creation of the universe.)

Why it's flawed: It's true that the seeming hospitability of the universe to the evolution of life has long intrigued physicists and biologists. Still, there are two ways to rebut this argument. First, it may be that the laws of nature are logically constrained; that is, they simply could not have taken on any other form than the one they have, not because of the whims of an Intelligent Designer, but because of the iron laws of mathematics. Second, many physicists today subscribe to a "many worlds" theory in which the laws of nature differ across trillions upon trillions of universes, and life only evolves in those universes where the parameters are just right. Assuming that premise, the fact that we live in one of those universes is pure chance, once again obviating the need for an Intelligent Designer.

"Specified Complexity"

The argument: Popularized in the 1990s by William Dembski, specified complexity is a fairly incoherent argument for intelligent design, but we'll do our best. Essentially begging the question, Dembski proposes that the strings of amino acids comprising DNA contain too much information to have arisen by natural causes, and therefore must have been designed. (By way of analogy, Dembski says, "A single letter of the alphabet is specified but not complex. A long sequence of random letters is complex without being specified. A Shakespearean sonnet is both complex and specified.") Dembski invents a concept, the "universal probability bound," for any phenomenon that has less than one in a googol chance of occurring naturally and therefore must be complex, specified, and designed.

Why it's flawed: Like the similarly sciency-sounding "irreducible complexity" (see slide #3), specified complexity is a theory supported by virtually no evidence. Basically, Dembski is asking us to accept his definition of biological complexity, but that definition is formulated in a circular fashion so that he's assuming his own conclusions. Also, scientists and mathematicians have pointed out that Dembski uses the words "complexity," "improbability" and "information" in very loose ways, and that his analyses of biological complexity are far from rigorous. You can gauge the truth of this accusation yourself by Dembski's widely disseminated rebuttal, that he is "not in the business of offering a strict mathematical proof for the inability of material mechanisms to generate specified complexity."

The "God of the Gaps"

The argument: Less a reasoned argument than an ad hoc assertion, the "god of the gaps" is a pejorative term to describe a resort to supernatural causes to explain features of the world we do not yet understand. For example, the origin of RNA (the precursor molecule to DNA) billions of years ago remains a major subject of scientific investigation; how could this complex molecule have assembled itself from a hot soup of minerals, amino acids, and inorganic chemicals? Legitimate researchers slowly, painstakingly collect evidence, propose theories, and debate the finer points of probability and biochemistry; intelligent design advocates simply throw up their hands and say RNA must have been engineered by some kind of intelligent entity (or, if they're willing to be more honest about it, God).

​Why it's flawed: ​You can write an entire book about the use of "god of the gaps" arguments in the wake of the Enlightenment, 500 years ago. The trouble for intelligent design advocates is that the "gaps" keep getting narrower and narrower as our scientific knowledge becomes more and more complete. For example, no less an authority than Isaac Newton once proposed that angels kept the planets in their orbits, since he couldn't think of a scientific way to handle gravitational instabilities; that issue was later resolved, mathematically, by Pierre Laplace, and that same scenario has repeated itself countless times in the fields of evolution and biochemistry. Just because scientists don't (currently) have an explanation for a particular phenomenon doesn't mean it's unexplainable; wait a few years (or, in some cases, a few centuries) and a natural explanation is bound to be discovered!