“Just a Theory”

“Just a theory”. That’s what people sometimes say in discussions about evolution. “Just a theory”, as if evolution is an idea some mischievous scientists thought up at happy hour. 


373px-Symbol_merge_discussion_svgWhen people use the word theory in casual conversation, they can mean almost any sort of explaination about anything no matter how speculative. We can have a theory about  what GM should have done to avoid bankruptcy.  I can have a theory about what’s wrong with the Royals this baseball season. We can have a theory about the secret group of international financiers who run the world.   I can have a theory about why my neighbor mows his yard at 7:30 am.

As we all know, words can have more than one meaning and more than one useage.  Let’s begin with the dictionary.

From Dictionary.com  “Theory”

1.a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein’s theory of relativity.


         2.   a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.


         3. Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.


          4.  the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.


          5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.


          6.  contemplation or speculation.


          7. guess or conjecture.

1. Theory, hypothesis are used in non-technical contexts to mean an untested idea or opinion. A theory in technical use is a more or less verified or established explanation accounting for known facts or phenomena: the theory of relativity. A hypothesis is a conjecture put forth as a possible explanation of phenomena or relations, which serves as a basis of argument or experimentation to reach the truth: This idea is only a hypothesis.

There are many correct ways to use the word “theory”. Today I want to think about what scientists mean when they say something is a theory.

A theory, in science is larger and more complex than you might expect.

Linus PaulingHere is how Linus Pauling explains scientific theory in his textbook, General Chemistry (Dover Publications:New York 1970 page 17)

… chemists and other scientists use the word theory in two somewhat different senses. The first meaning of the word is … a hypothesis that has been verified. The second use of the word theory is to represent a systematic body of knowledge, compounded of facts, laws, theories in the limited sense describe above, deductive arguments and so on.  Thus by the atomic theory we mean not only the idea that substances are composed of atoms, but also all the facts about substance that can be explained and interpreted in terms of atoms and the arguments that have been developed to explain the properties of substances in terms of their atomic structure.

Now we need to define two other terms, “hypothesis and Scientific Law.

A hypothesis is a statement that explains some facts and is subject to testing to determine its plausibility.  It is a provisional answer to a particular question. It needs to be testable and falsifiable. That’s a key concept. In science we don’t try to prove something is true, we try to prove it is false.  Scientists look for where the idea is weak or wrong. Finding an weakness or error does not necessarily mean the hypothesis is scraped- it might; more often the hypothesis needs to be modified. The goal is to remove a much doubt about the hypothesis as we can, to make it as accurate as possible.

A scientific law is a hypothesis that is assumed to be universally true. A law has good predictive powers, allowing a scientist to model a physical system  and predict what will happen under various conditions. ( The American Heritage Science Dictionary, new updated edition:2008 , Houghton Mifflin Harcourt Publishing Company)

As Linus Pauling points out (page 14) laws themselves can be found to have limited validity.  New information may cause a law to be modified.

One of the important points here is that laws and theories are neither iron clad nor cast in stone. As new information is gathered, theories need to be modified. Sometimes the modifications are minor, sometimes they are larger.

The other important point is that a theory (as in Pauling’s second use) rests on a very large body of evidence and can be used to make accurate predictions.

Both these points are true. Theories are developed from a large body of information and theories can be modified.

Sometimes people assume that there is an end point where science is “finished”. It is for the most part an unspoken assumption because, of course, if you think about it there are obviously many things we don’t understand completely.

Because new discoveries are made and older concepts are modified does not mean that the basic theory is flawed beyond use.  Science is a continual process of refinement. The fact that scientists may disagree about a portion of a very large and complex theory doesn’t destroy the entire theory. The disagreement helps refine and improve the theory, it is a movement toward greater accuracy. The process isn’t linear. It isn’t tidy. It can be confusing. 

To dismiss the theory of evolution as irreparably flawed because it has been and will continue to be modified is to misunderstand how science works. For example, in my work as a veterinarian often, perhaps even most of the time, people expected a degree of certainty in a diagnosis and a prognosis that just wasn’t possible. Now, we can be very sure about some diagnoses and treatments but the margin of error- that grey area- never entirely goes away. That doesn’t mean we decide that medicine is untrustworthy or deceptive or false. It doesn’t mean we need to recognize its limits as well as its strengths.

I suppose this all might sound like I am arguing both sides of the issue. But what I want to do is offer a more realistic and complex understanding about how science works. The theory of evolution rests on a very large body of evidence and new information may cause scientists to modify the theory. That is the way science works.  The theory of evolution ( or any other theory) is a complex set of ideas that we will never be finished modifying.  There is always something new to learn. There are levels of complexity and intricacy to be discovered that we can’t begin to  imagine. That is what is so wonderful about science.

I’d like to know, what do you think?

2 thoughts on ““Just a Theory”

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