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Is “Evolution” a “Theory” or “Fact” or Is This Just a Trivial Game of Semantics? (Part 2)

Casey Luskin

[Editor’s Note: This is a Part 2 of a 5 part series on whether evolution should be called a “theory” or a “fact.” See: Part 1, Part 2, Part 3, Part 4, Part 5. The full article can be found here.]

In Part 1, I assessed the question of whether Darwinists are correct to define theory as a “well-substantiated scientific explanation of some aspect of the natural world” or a “comprehensive explanation of some aspect of nature that is supported by a vast body of evidence” (the hard definition of theory). I found that they are correct to use such a definition, but that Darwinists sometimes overly downplay the fact that theory can also legitimately mean merely “a proposed explanation whose status is still conjectural,” “contemplation or speculation,” or “guess or conjecture” (the soft definition of theory). As I observed, Darwinists are also wrong to imply that scientists never use the term “theory” to mean “a proposed explanation whose status is still conjectural.”

Previously I quoted Bruce Charlton, editor-in-chief of the journal Medical Hypotheses, observing that “[a]n old joke about the response to revolutionary new scientific theories states that there are three phases on the road to acceptance: 1. The theory is not true; 2. The theory is true, but it is unimportant; 3. The theory is true, and it is important — but we knew it all along.” Charlton goes on to contend that those who propose new revolutionary theories face difficult battles:

The defining feature of a revolutionary theory is precisely that it seeks to replace the assumptions of an already-existing theory — so a new theory cannot be evaluated on the basis of the assumptions of the old theory. This is why a new and revolutionary theory will almost invariably strike people as false. … The path to fame as a theorist surely is long, winding and replete with pitfalls.

It seems clear that scientists can use the word “theory” to mean “conjecture,” but it is also fair to say that typical circumstances, when scientists say “theory,” they mean the hard usage of the term: “a more or less verified or established explanation.”

This thus leads to the question, under such a strong definition of the term, does evolution qualify as a theory?
Assuming that we are using the hard definition of theory, different people will give different answers to that question. Under such an understanding of the term, if we define theory as “a more or less verified or established explanation,” then theory is in the eye of the beholder. Darwin-skeptics will not agree that neo-Darwinian evolution is “a more or less verified or established explanation.” But Darwinists will agree. So the question over whether neo-Darwinian evolution should be called a “theory” is not the core question of this debate. A better question would be: “Is neo-Darwinian evolution ‘a more or less verified or established explanation’?”

Darwinists have the right to believe that neo-Darwinian is a verified and established explanation–i.e. that it meets the hard definition of theory. But they do not have the right to insist that Darwin-skeptics must call evolution a “theory,” so defined. While Darwinists are correct that the technical definition of “theory” means a well-established and verified explanation, they should not insist that evolution can never be called “just a theory.” When they do this, they are actually imposing onto the debate their conclusion that evolution must be considered by all to be a verified and established explanation. Were they to tolerantly allow Darwin-skeptics to dissent from the orthodox neo-Darwinian position, Darwinists would not insist that Darwin-skeptics entirely abandon the phrase “evolution is just a theory.”

However, given that the technical, scientific, hard definition of theory does typically mean a well-established and verified explanation, then it is best if Darwin-skeptics take the high road and avoid calling neo-Darwinian evolution “just a theory.” And as we shall see in the next installment of this series, the question “is evolution a ‘more or less verified or established explanation'”? is also a complex question, for it can also depend on the definition of “evolution.”


Casey Luskin

Associate Director, 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.