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Casey Luskin Scientist and Public Defender of ID

How Do We Know Intelligent Design Is a Scientific “Theory”?


A question I commonly receive is whether intelligent design is a “scientific theory.” The word “theory” gets tossed around a lot as if everyone agrees on what it means. To answer the question, we must first consider the meaning of the word “theory.”

As I’ve already elaborated here, philosopher Peter Kosso explains that calling something a “theory” says little about the degree of certainty backing the idea. As he states, “neither ‘theoretical’ nor ‘law’ is about being true or false, or about being well-tested or speculative.” In Kosso’s view, a theory “describes aspects of nature that are beyond (or beneath) what we can observe, aspects that can be used to explain what we observe.” Thus “[s]ome theories are true (atomic theory), some are false (caloric theory), and the scientific method is what directs us in deciding which are which.”

Does ID meet this definition of theory? Yes, it does.

ID is a theory of design detection, and it proposes intelligent agency as a mechanism causing biological change. ID allows us to explain how aspects of observed biological complexity, and other natural complexity, arose. And it uses the scientific method to make its claims.

The scientific method is commonly described as a four-step process involving observations, hypothesis, experiments, and conclusion. ID begins with the observation that intelligent agents produce complex and specified information (CSI). Design theorists hypothesize that if a natural object was designed, it will contain high levels of CSI. Scientists then perform experimental tests upon natural objects to determine if they contain complex and specified information. One easily testable form of CSI is irreducible complexity, which can be tested for by reverse-engineering biological structures through genetic knockout experiments to determine if they require all of their parts to function. When scientists experimentally uncover irreducible complexity in a biological structure, they conclude that it was designed.

Meeting the Definition of “Theory” from ID’s Most Eminent Critics

Though Peter Kosso might disagree, I believe ID qualifies under his definition of “theory.” But as I suggested above, there are many definitions of “theory” out there. How can we know if ID is a scientific theory? Take the definition of “theory” given by ID’s most eminent scientific critics, and if ID meets that definition then there’s a good bet ID may properly be considered a scientific theory.

Perhaps the most eminent scientific opponents of the theory of intelligent design can be found among the membership of the U.S. National Academy of Sciences (NAS). In contrast to Peter Kosso, the NAS defines “theory” as an idea that is well-tested and well-supported by the scientific evidence:

  • “a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, and tested hypotheses” (Science & Creationism: A View from the National Academy of Sciences (National Academy Press, 1999).)
  • “a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence” (Science, Evolution & Creationism (National Academy Press, 2008).)

Even if we accept the NAS’s more stringent definition of theory, ID more than qualifies.

When we’re confronted with multipart tests, it’s often useful to break them down into their elements. If the subject meets all the “elements,” then it passes the test. Let’s use that method here to analyze whether ID is a theory:

  • Element 1: ID must be an “explanation of some aspect of the natural world” and a “comprehensive explanation of some aspect of nature.”
  • Element 2: ID must “incorporate many facts, laws and tested hypotheses.”
  • Element 3: ID must be “well-substantiated” and “supported by a vast body of evidence.”

Element 1: ID is a an “explanation of some aspect of the natural world” and a “comprehensive explanation of some aspect of nature.”

ID is not just an explanation of “some aspect of the natural world”: in fact it explains many aspects of the natural world. If we think in terms of just broad categories, ID proposes that intelligent agency is the best explanation for historical events like:

  • the origin of the fine-tuning of the cosmos for advanced life.
  • the origin of extremely high levels of complex and specified information in DNA.
  • the origin of integrated systems required for animal body plans.
  • the origin of many irreducibly complex systems found in living organisms.

So ID satisfies this element: It is an explanation of many aspects of the natural world, especially many aspects of biological complexity.

Element 2: ID “incorporates many facts, laws and tested hypotheses.”

ID easily meets this criterion. ID incorporates many facts, laws, and tested hypotheses, including:

  • ID incorporates the known laws and constants of the universe and ties them together in a unified theory to explain why they are coordinated to produce life-friendly physical parameters.
  • ID incorporates many known facts about DNA sequences, as well as tested hypotheses showing they are finely tuned to perform biological functions.
  • ID incorporates a myriad of tested hypotheses about the geologically abrupt appearance of body plans in the fossil record, as well as numerous facts from biochemistry and animal biology regarding the kind and amount of integrated information necessary to coordinate new types of proteins, cell types, tissues, and organs into new functional body plans.
  • ID incorporates many tested hypotheses about the presence of irreducible complexity in biological systems, evidenced by genetic knockout experiments which have shown that irreducible complexity is a real phenomenon.
  • ID does all of this by proposing new laws such as the law of conservation of information, new principles about the causes of high CSI, new methods of measuring functional information and complexity, and new hypotheses about the ubiquity of fine-tuning throughout both cosmology and biology.

Element 3: ID is “well-substantiated” and “supported by a vast body of evidence.”

This element is unique because it places “theory” in the eye of the beholder. If you think ID is correct (i.e., “well-substantiated”), then it will qualify as a scientific theory. If you don’t think it’s correct, then you won’t think it’s well substantiated, and ID won’t qualify as a theory. In practice, this element thus measures subjective questions about what people believe about an idea rather than posing objective questions about the basic nature of the idea being considered. This is probably why careful thinkers like Peter Kosso expressly exclude this element from their definition of “theory.”

Nonetheless, ID meets the NAS’s third element, and a vast body of evidence can certainly be shown to back intelligent design. ID is well substantiated because a significant number of studies have confirmed ID’s predictions, such as:

  • Studies of physics and cosmology continue to uncover deeper and deeper levels of fine-tuning. Many examples could be given, but this one is striking: the initial entropy of the universe must have been fine-tuned to within 1 part in 10(10^123) to render the universe life-friendly. That blows other fine-tuning constants away. New cosmological theories like string theory or multiverse theories just push back questions about fine-tuning, and exacerbate the need for fine-tuning.
  • Mutational sensitivity tests increasingly show that DNA sequences are highly fine-tuned to generate functional proteins and perform other biological functions.
  • Studies of epigenetics and systems biology are revealing more and more how integrated organisms are, from biochemistry to macrobiology, and showing incredible finely-tuned basic cellular functions.
  • Genetic knockout experiments are showing irreducible complexity, such as in the flagellum, or multi-mutation features where many simultaneous mutations would be necessary to gain an advantage. This is more fine-tuning.

ID is supported by a vast body of evidence ranging from physics and cosmology to biochemistry to animal biology to systems biology to epigenetics and paleontology. ID more than exceeds the NAS’s definitions of “theory.”

Casey Luskin

Associate Director and Senior Fellow, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.