Merely a Theory?


I would like to take this opportunity to explain something that is consistently being repeated incorrectly by certain members in our society, that “Evolution is only a theory!”

In a discussion moderated by anchor Miles O’Brien on CNN, Christine O’Donnell squared off against Michael McKinney, a University of Tennessee professor of evolutionary biology. Not only was O’Donnell in favor of teaching creationism alongside evolution, but she wasn’t even sure evolution was real. According to a transcript:


Evolution is a theory and it’s exactly that. There is not enough evidence, consistent evidence to make it as fact, and I say that because for theory to become a fact, it needs to consistently have the same results after it goes through a series of tests. The tests that they put — that they use to support evolution do not have consistent results. Now too many people are blindly accepting evolution as fact. But when you get down to the hard evidence, it’s merely a theory. [1]

I apologize for picking on Ms. O’Donnell, but her position of influence is the perfect reason why I need to clarify a few things.

Let’s take a quick look at what “theory” means. The Oxford English Dictionary gives two meanings (actually more, but these are the two that matter here)

Theory, Sense 1: A scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena; a hypothesis that has been confirmed or established by observation or experiment, and is propounded or accepted as accounting for the known facts; a statement of what are held to be the general laws, principles, or causes of something known or observed.

Theory, Sense 2: A hypothesis proposed as an explanation; hence, a mere hypothesis, speculation, conjecture, an idea or set of ideas about something; an individual view or notion.

Obviously, the two meanings are quite different from one another. The short answer is that scientist and those who are part of the intellectual community are using Sense 1; while Ms. O’Donnell is – perhaps mischievously, or sincerely – opting for Sense 2.

For some reason, people seem to confuse the word “theory” with “hypothesis” all the time, which leads me to the following question: How do you feel about the theory of gravity?

Yes, gravity is actually a theory in pretty much the same way that evolution is a theory. Does anyone out there doubt the power of gravity? Go ahead, throw yourself out the window and tell me what happens. If it’s “merely a theory”, you shouldn’t worry about anything, right?

The reason you won’t gamble with your life is because you are mostly certain that the theory of gravity is pretty solid. Basically, we are assigning different meanings to the same word. One must remember that when a scientist, technician, or mathematician uses the word theory, they are using it in sense 1 (see above).

Theories are essentially hypotheses that have been so thoroughly tested and confirmed (through experiments designed to disprove them) and so well established that new evidence is not likely to contradict them. The difference between a theory and a hypothesis is the (very large) degree of confidence we have in its validity and power to explain. When someone says: “It’s only a theory” they are most likely using the word colloquially and not scientifically.

Just to close the loop on gravity, there is Newton’s Law of Universal Gravitation that describes the attraction between all bodies with mass, and there is Einstein’s theory of General Relativity, which explains gravity and, in fact, supersedes the Law of Universal Gravitation in its scope. According to the General Theory of Relativity, gravity is a consequence of the curvature of space-time which governs the motion of inertial objects. The simpler Newton’s law of universal gravitation provides an accurate approximation for most calculations.

So in a nutshell, there is a law of Gravity, and there is a theory that explains it.

Now, back to the subject at hand…

I’m not here to debate why a U.S. Senate nominee does not know the difference between a hypothesis and a theory (that’s for another time). I’m here to simply ask: Why are we so certain about the theory of gravity but have doubts about the theory of evolution?

Once you realize that Evolution completely destroys all religious arguments, you’ll understand why it’s constantly under attack.  It’s all a play on words, a beautiful dance between a very defensive institution and the ignorant minds that support it.

Next time someone talks about evolution only being a theory; please make sure to ask them what they think about the theory of gravity. I promise it will make for a very interesting conversation.

Thanks for reading,


  1. GOP’s Delaware Senate Nominee Christine O’Donnell Not a Big Fan of Evolution:
  2. Oxford English Dictionary:

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