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No. 1531:
Only a Theory

Today, let's theorize. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

A listener left a phone message. I'd mentioned Darwin's theory of evolution, and he said, "Wait a minute; Darwin's theory wasn't about evolution. His theory was that evolution occurs by means of natural selection." Warning flags went up. There was more here than met the eye. When I turned to dictionaries I saw the problem more clearly. The word theory has shifted under our feet.

The classical dictionary definition says that a theory is a mental plan or a systematic set of principles. A theory, unlike a hypothesis, has been verified. It has been shown to fit the facts, and it has stood up against attempts to prove it false. The atomic theory of matter and Einstein's Theory of Relativity are good examples. All the older dictionaries tell us that we're talking slang when we use the word theory for a hunch or a guess.

But that changes in dictionaries of current usage. They tell us that a theory is a belief or a proposal or a hypothesis. Theoretical knowledge now means a tentative idea and one that's been divorced from practice. The old meaning -- an established body of intellectual understanding -- withered while I wasn't looking.

What Darwin proposed was not that evolution occurs -- it obviously did. He set out to explain why it occurs. He explained how natural selection works. I expect that caller wanted me to be more cautious in a world where you hear people saying "Evolution is only a theory!" Evolution, of course, has long been a theory in the old sense of the word. But to call it a theory today is to scoff at it.

Few people still use the word theory in its old sense, and we have no new word to replace it. Meanwhile, fields like math, physics, and engineering absolutely depend on intellectual constructs. To work in them, you have to traffic in theory. Yet, according to current usage, to be a theoretician is to be vague and ineffective.

All this has a chilling effect in our schools. Arithmetic, math, and science now have to be results-oriented. Subjects that're inherently theoretical (in the old sense of the word) are being stripped of their theoretical subtlety. Students can smell that subtlety a mile away. They sense that they can shrug it off when the teacher tries to introduce it. Textbooks try to teach science by presenting solved examples rather than asking students to deduce their own results.

We need to do something about all this. We need to make analytical deduction respectable again. So here's what I ask of you: The next time a friend voices suspicions about something, and you find yourself starting to say, "That's only a theory," stop and bite your tongue. Save that fine word theory for established knowledge. Save it for things like the photon theory of light, evolution by natural selection, or the laws of thermodynamics. Reserve the word theory for established structures of knowledge. And give our students a chance to see the kind of subtlety that turns isolated facts into whole bodies of understanding.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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