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

Many intelligent people use the “evolution is just a theory, not a fact” line–but they immediately get into trouble because, as I discussed in Part 1, the formal scientific definition of theory is typically understood to mean a “well-substantiated scientific explanation of some aspect of the natural world.” In other words, when talking to a scientifically minded crowd, calling evolution “just a theory” is not a good way to express scientific doubts about neo-Darwinism. As I noted in a previous post, an article recently in The Scientist observed that, “public discontent with classical evolution as an inclusive theory stems partly from an intuitive appreciation of its limits.” Thus those who call evolution “just a theory, not a fact” are trying to communicate some legitimate underlying truth about their scientific criticisms of neo-Darwinism. They are simply using poor terminology to communicate their point.

Sadly, Darwinists often then ridicule or scold Darwin-skeptics who use the “evolution is just a theory, not a fact” line by treating them as ignorant or uninformed regarding the proper definition of theory. Let’s explore what people really mean when they say “evolution is just a theory, not a fact,” and then I’ll offer some final advice regarding how Darwin-skeptics can effectively communicate their doubts about Darwin.

All I wanted to say is that I’m a scientific skeptic of neo-Darwinism. How can I convey such skepticism without getting stepping on a semantic land mine and getting scolded by Darwinists?
Great scientific claims must be backed by great scientific evidence. When most people claim that “evolution is just a theory, not a fact,” what they really mean is that there is not convincing scientific evidence to justify the great claim that all life is related through universal common ancestry and that it evolved via an process of unguided natural selection acting upon random mutation. Doubts about neo-Darwinian evolution might stem from:

• The failure of evolutionary biology to provide detailed evolutionary explanations for the origin of complex biochemical features (see Opening Darwin’s black box for a brief discussion);
• The failure of the fossil record to provide support for Darwinian evolution; (see The abrupt appearance of biological forms or Punctuated Equilibrium and Patterns from the Fossil Record for discussions);
• The failure of molecular biology to provide evidence for universal common descent; (See Barking up the Wrong Tree for a brief discussion);
• The failure of genetics and chemistry to explain the origin of the genetic code; (see Problems with the Natural Chemical “Origin of Life” (updated) or The origin of life remains a mystery for discussions);
• The failure of developmental biology to explain why vertebrate embryos diverge from the beginning of development. (see Evolving views of embryology for a discussion).

But how does one simply communicate such viewpoints without getting into semantic trouble? As I explained in Part 4, I don’t recommend one-liner sound-byte arguments against evolution because they don’t communicate anything about the content of the scientific deficiencies of neo-Darwinism. Here’s why:

When someone says “evolution is just a theory,” it sounds like the speaker cannot cite actual scientific evidence against evolution, and that the only objection the speaker can muster is based upon appealing to postmodern rhetoric which asserts that we really can’t know if anything is true. The truth is that science is capable of studying the validity of historical scientific theories such as neo-Darwinism, but the “evolution is just a theory” line makes it sound like the speaker is not interested in studying or discussing that evidence. In the debate over evolution, discussions of evidence are what matter most. As stated previously, calling something a theory doesn’t necessarily tell you about the state of the evidence. The best way to express dissent from evolution is to actually discuss its failure to explain the scientific evidence.

The “evolution is just a theory” line can come off as if the speaker really thinks “evolution is just a guess, so I don’t have to believe it if I don’t want to.” In fact, neo-Darwinian evolution as a whole is not merely a guess and most Darwinian scientists will provide reasons why they think it is the best explanation for the diversification of life. If you’re like me, and you think that neo-Darwinian evolution has scientific problems, then you should be able to provide reasons beyond stating “it’s just a theory.” As noted above, the best strategy is for you to be prepared to give a few specific scientific reasons why you question Darwinian evolution.

But if you really must use short, one-liner sound-bytes to describe doubts about neo-Darwinian evolution, here is my advice: As we learned in Part 1, the technical definitions of theory do indeed mean “a more or less verified or established explanation,” whereas a hypothesis has the meaning of “a conjecture put forth as a possible explanation.” In this sense, when evolution is defined to include both universal common descent and a driving force of natural selection acting upon random mutation to produce the complexity of life (i.e. neo-Darwinian evolution), for Darwin-skeptics like me, such evolution is not a theory, nor is it fact. It is “just a hypothesis.”

But as I noted above, it’s best to give more information than one-liner sound-bytes. So I don’t recommend that Darwin-skeptics go around saying “evolution is just a hypothesis,” even though such a phrase would more-accurately use the technical definitions of “theory” and “hypothesis.” What follows is a slightly longer description of what one might say to communicate doubts about neo-Darwinism without falling into soundbyte arguments:

When evolution is defined as mere change over time within species, no one disputes that such evolution is a fact. But Neo-Darwinian evolution–the great claim that unguided natural selection acting upon random mutations is the driving force that produced the complexity of life–has many scientific problems because such random and unguided processes do not tend to build complexity. According to the technical definitions of “theory,” “fact,” and “hypothesis,” neo-Darwinian evolution is neither theory nor fact. It’s just a hypothesis.”

Closing Thoughts
In the end, my final advice for everyone is this: Whether you think “evolution” is “fact,” “theory,” or “hypothesis,” or some combination thereof, it’s important to use all of these terms carefully and if possible, define them when you use them. It’s also important to have patience with those who may misuse these terms, for each of these terms can have multiple meanings, allowing ample opportunities for confusion and miscommunication in this highly-charged debate.