What is a Theory?
Updated: Nov 3, 2019
There seems to be some confusion about what exactly a "theory" is in science. Some states have tried to get stickers put on textbooks that emphasize evolution is only a theory while opponents argue that the definition of the word "theory" is much more akin to "fact" than "possibility" or "hypothesis." I've had conversations with people who point to internet memes like the one pictured here to "shame" anyone who disagrees with them. But the reality is, theory is a slippery word and seems to mean different things in different contexts, even within science. But let's start with the official definitions as we'll see that the problem starts in the dictionary.
1. an idea or set of ideas that is intended to explain facts or events 2. an idea that is suggested or presented as possibly true but that is not known or proven to be true 3. a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena <the wave theory of light> 4. a hypothesis assumed for the sake of argument or investigation 5. a body of theorems presenting a concise systematic view of a subject <theory of equations> You can already see why there is confusion just looking at the nuanced definitions, but it gets worse. You get internet meme definitions thrown in from laymen armed with misinformation and you get different connotations from different branches of science as well. For example, when a skeptic uses the word "theory" to describe evolution, an opponent will, almost without fail, quip that gravity is only a theory as well and then ask the skeptic if they believe in gravity. This is a straw man argument however because gravity is not a theory, but an observable, testable and repeatable phenomena. The theory of gravity is the scientific attempt at explaining this phenomena (reference above definitions again). The truth is, we don't know how gravity works- we have some theories, we have some models, but they have not been verified and they may or may not be accurate and the vast majority of scientists will admit as much. Now let's take a look at another use of the term in science as a qualifier, such as in a theoretical physicist. Notice this title differentiates this type of physicist from regular physicists. Why? Because regular physicists are dealing with empirical science while theoretical physicists are not. Once again the term theory implies something which is not yet proven (or even provable) and yet when it comes to evolution, advocates want the word theory to carry a sense of much more authority and concreteness. Yet in even the comical internet meme we can clearly see that "facts" are not concrete in science and may be modified or entirely discarded in light of new evidence. So even by this definition a theory aligns best with dictionary definition #2- being one possibility but not proven. But possible and plausible are not synonymous. Even if a theory can be deemed possible, it then must be evaluated to conclude whether or not it is plausible. In this process, a scientific truism called Occam's Razor comes into play as well as mathematical probabilities. How does evolution stack up here? Not very well it turns out. Science has yet to even offer evidence that evolution is possible, let alone plausible. In fact, after two centuries of evolutionary investigation, evolution seems less possible now than when Darwin (et al) first submitted the hypothesis. We have less answers and more speculation. The key mechanism, the linchpin of the theory, is random mutation. Without this theorized engine, evolution is not possible. Gene pool shift and natural selection can cause diversity within a species but only random mutation can create new genetic information- in theory. In observable, testable, repeatable and falsifiable empirical science however, random mutations have done no such thing despite numerous attempts by very tenacious scientists. Not only have they had zero success, they've actually discovered more and more evidence that random mutation actually cannot do what they theorized it must do (see here). Then we come to the question of plausibility. Let's use dictionary definition #4 for a minute and simply assume evolution is possible for the sake of investigation. If we were to get over the hurdle of possibility, would evolution pass muster in the next step? Not at all- mathematicians and statisticians have long been the enemy of evolutionists. The probability of evolution happening is effectively zero. Even evolutionists acknowledge this fact which is why string theory and multiverse ideas are popular- if there are an infinite number of universes in existence, then the probability of evolution occurring in one of them goes from being statistically zero to statistically inevitable. But is there any empirical evidence for parallel universes or string theory? No. It's all theoretical and mostly unprovable. The evidence we do have is detrimental to evolutionary theory, so we have to hypothesize creative ways to get around that inconvenient fact. This leaves us with one last definition that seems to apply to the term theory- general acceptance (part of definition #3). This of course falls prey to the appeal to popularity logical fallacy (most believe it, so it must be true) or even worse, the appeal to authority fallacy (scientists are infallible, therefore what they say must be true). An obvious example of this fallacy can be seen in the current global warming debate: Whenever scientific evidence contradicting the status quo is presented, rather than refuting the evidence, the messenger gets lambasted with the knee-jerk response, "97% of scientists agree!" or "The science is settled!" Never mind the fact that the 97% number is fraudulent or that by definition science is never settled- this argument is inherently flawed in that truth is not determined via a democratic process as the laws of the universe do not conform to popular opinion. So, in the end, is evolution a theory? Yes and no- it depends on which definition you're using. Is it an idea that is intended to explain facts or events (the fact that the universe and life exists)? Yes. Is it an idea that is presented as possibly being true but that is not known or proven to be true? That depends on who you're asking- many laymen and scientists alike present evolution as being proven to be true while others acknowledge the lack of empirical evidence. Is it a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena? No, it is not plausible without invoking hypothesized infinite universes, but yes, it is generally accepted. Is it a hypothesis assumed for the sake of argument or investigation? Absolutely. We've spent two hundred years assuming it to be true and building complex systems, models and mythology around an idea which we have zero empirical evidence for. Is it a body of theorems presenting a concise systematic view of a subject? Yes, it is probably the most systematic view in science today. Concise? Not exactly- it's enormously complex and convoluted. So we've established that by and large calling evolution a theory is not a misuse of the term. However, by now it should be equally obvious that a theory is not fact nor is it even necessarily well substantiated. A theory is a possible explanation of fact but that does not make the theory itself fact. To complicate matters, in science an idea never really graduates from the theory phase- it simply becomes a more plausible and/or accepted theory. There are highly tenuous theories in science and there are theories which are regarded as gospel truth. Evolution definitely sits in the latter category however, despite the lack of empirical evidence to justify such dogmatic acceptance. If you've made it this far, you're probably wondering if things should be clearer at this point. The truth is, probably not. But I hope you now have a better understanding of the problem and the arguments. Those who accept the evolutionary explanations of how the universe came to be have a tendency to think their belief is a product of scientific fact rather than an ideology founded squarely on faith. They call their views scientific and they want the concreteness of empirical science to be associated with their beliefs. But wishing does not make it so and intellectually honest scientists have stated as such many, many times. "Evolutionists have "Physics Envy." They tell the public that the science behind evolution is the same science that sent people to the moon and cures diseases. It's not. The science behind evolution is not empirical, but forensic. Because evolution took place in history, its scientific investigations are after the fact—no testing, no observations, no repeatability, no falsification, nothing at all like physics. . . . I think this is what the public discerns—that evolution is just a bunch of just-so stories disguised as legitimate science." - John Chaikowsky, "Geology v. Physics," Geotimes (vol. 50, April 2005), p. 6 "I certainly don’t want any intrusion of religious ideas in the name of science — but I don’t want this bland soup that’s taught as evolution in the name of science, either. It’s not science — it’s catechism." - Carl Woese, "Famed Microbiologist on Teaching Evolution: Don't Start Until College," Wired Science, Feb 22, 2008