"Yeah well, it's just a theory".
Seven words that make my blood boil.

This same point has been made in every evolution-creation debate there has ever been, and it provokes the same exasperated response from the evolution camp every time.

"Evolution is both a fact AND a theory. You're misunderstanding scientific terminology. What about the theory of gravity; if you don't believe it then you don't just float away!"

The problem is based on the dichotomy between the colloquial use of the word theory and the scientific use. This is a dichotomy that the public is not generally aware of. Many are sympathetic to the idea of teaching evolution side by side with creationism because "after all, aren't they both theories"?

It's not just a disjunct, however. The two definitions of the word are diametrically opposed. 

1. A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.
6. An assumption based on limited information or knowledge; a conjecture.

What has brought this on, you may ask? Well, my article last week was about the most irritating words used in reporting evolution stories in the media. I received an email from Larrie  D Ferreiro who argues that actually, the most irritating term using in discussion evolution stories is the prefix "theory", which is like painting a big, red target on ourselves. As he puts it, perhaps we should think about removing their weapon of choice.

From: Dr. Larrie D. Ferreiro
To: Oliver Knevitt
Subject: The most irritating term in evolution reporting is THEORY 
Dear Dr-to-be Kneviit,
By way of introudction, I'm a UCL and Imperial College London grad, PhDin history of science, technology and engineering.   My recent book "Measure of the Earth" (Basic Books, 2011) describes an 18th century Geodesic  Mission to the Equator to determine the true shape of the Earth, and at the same time prove or disprove Newton's laws.  
I argue that the most irritating term in evolution is the use of the phrase "theory of evolution", instead of "law of evolution".  Why do biologists and paleontologists continue to paint a huge, flashing target on their profession by using the term "theory of evolution", i.e., inviting criticism by allowing creationist and anti-science opponents to focus on the word "theory"?  There is a perfectly acceptable alternative, "law of evolution", which, etymologically speaking, would stop many (not all) arguments dead in their tracks. 
The precedent for this is, of course, the "theory of gravity", in which Newton's ideas of attraction were opposed both politically and by those with the religious conviction that it eliminated the hand of God -- they preferred the great, swirling ether of Descartes, which he claimed had been set in motion through divine action (this was all c. 1720-1745).  Newton's ideas won out, not merely because the science had proved it correct (the Geodesic Mission I mentioned was part of that), but because the political landscape changed -- and in part because scientists were by then using the phrase "law of gravity".  
Today, we don't call it the "theory of gravity" -- we call it the "law of gravity" because it fits the facts as nothing else.  Evolution has long since been proven to fit the facts, so I argue that we need to start using the word "law" instead of "theory".  We also refer to various other theories as "laws" -- Newton's laws, Maxwell's laws, Ohm's law, etc.  so there is ample precedent for throwing away "theory" and replacing it with "law".   Yes, it may be scientifically proper to say "theory", but the political anti-science wing latches on to "theory" as the road to doubt, and politics trumps science every time.   
Dr. Larrie D. Ferreiro

So. Is this an intractable problem? Stephen Jay Gould wrote about what we mean by theory extensively, and of course, the ideal situation would be for widespread teaching of the difference. If we taught the theory of evolution from the ground up, and from an early age, then people would not fall for such vacuous statements.

But this is wishful thinking. It seems likely that we will persist with high school biology taught without reform for some time as it is: a hobbled together mishmash of case studies and bastardized explanations. Without a coherent and unified teaching of biology, centred around evolutionary theory, the general public will continue to treat evolution as almost akin to hypothesis, and doubt it. Not, I should reiterate, just doubting that natural selection is the theory that explains evolution; instead doubting that evolution itself occurred, it being a mere hypothesis to explain life.

Perhaps the question boils down to this. Do we think that public disenfranchisement with evolution is sufficient cause to change our definitions?

If so, and we decide that theory is an tainted and schizoid word to be junked, then there are two alternative words we can use to describe evolution. We could instead refer to it as evolutionary science or as the law of evolution.

The first option is, semantically speaking, less destructive. We're not bending definitions here; evolutionary theory really is a mix of facts and testable explanations.

However, the term "evolutionary science" is undeniably somewhat underwhelming. it is rather vacuous, because it doesn't really have a formal definition like theory does. I can put my finger on why it is so unappealing. It feels a little like a me-too move. After all, we have creation science and creation scientists. Yes it's an abhorrent use of the word, but to me it still feels like we're legitimising them by setting ourselves up as an equal opponent. So, unfortunately, I don't think this would solve the problem.

The second option, however, really plays with how we should accurately define evolution. Can we really call evolution a law? Colloquially, we refer to gravity as the law of gravity. So why not the law of evolution?

Here, we have the same issue that we had with the word theory, except that the colloquial definition is not the polar opposite of the philosophical one. Collquially we think of a law as rule; a decree that is never broken. The philosophical definition, which is something which many debate over, is something akin to a set of rules that link facts.

Evolution aside, you probably won't be surprised to learn that many have pondered whether natural selection can be termed a law. Ultimately, it still needs to be testable to be a law. Personally, I'm happy to call natural selection a law. Here's why.

A law must be able to say that given a certain set of conditions, the outcome we get arises according to a particular function of parameters. So, in natural selection, our starting conditions are replicating entities having heritable variations in a competitive environment. The outcome is increased fitness of the entities. The function is the adaptive design and environmental variables.

The key here is that it is not sufficient to say that if we have the perfect conditions for natural selection then wherever the conditions apply, natural selection results. Instead, the way I've laid it out, based on reading this paper (paywalled, sorry), it means that we have a framework that is testable and predictive. In other words, we have a law of natural selection.

When we talk about evolution as a whole though, I think we lose this rigidity. This may be a banal point, but what about extinctions? The best way to look at it, I think, is that evolutionary theory is a mosaic of facts and testable explanations, laid on the foundations of the law of natural selection; the most important force in evolution (but not the only one). We would lose some of this nuance if we went the whole hog and called it the law of evolution. 

This is not to mention that the philosophers would probably disown us. We can't have a special use of the word law just for evolution. It's also not feasible to have one rule for us scientists, the "ones in the know", and another rule for the members of the public. It would not help our cause if we undermined their trust.

So let's again return to the question. Is public disenfranchisement with evolution sufficient cause to change any definitions?

Begrudgingly, I'd have to say no. I'm no philosopher, but I don't think law really does justice to what evolutionary theory is. In a way, the word law is just too boring and doesn't capture the breadth of different ideas that surround evolution. Let's face it: gravity is boring. It's the sort of thing that deserves to be called a law. If evolution were a law, it would be choc-a-bloc with caveats and exceptions. It simply doesn't capture the unprectiveness, nuance, and expanse of evolution.

Which means that we're still in the intractable situation we were in before, or rather, now. Unless anyone else disagrees, of course, in which case, I'd like to hear your thoughts.