5X5 Episode 65

5X5 Episode 65
Scientific Theory
16th April 2009
5X5 64	5X5 66
Skeptical Rogues
S: Steven Novella
B: Bob Novella
J: Jay Novella
E: Evan Bernstein
Guest
M: Mike Lacelle
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Skepticism 101 - Scientific Theory

Voice-over: You're listening to the Skeptics' Guide 5x5, five minutes with five skeptics, with Steve, Jay, Rebecca, Bob and Evan.

S: This is the SGU 5X5. Mike Lacelle is sitting in for Rebecca Watson this week, and we are talking about the nature of scientific theory. Now the term theory is used in science to refer to a very specific thing: a set of ideas and claims, an explanatory model that brings together multiple lines of evidence, woven together into one over-arching explanation. It's distinguished from a hypothesis in that a hypothesis is a much more narrow thing. A hypothesis is essentially a guess. It is one notion about one specific claim or what you think the outcome of a specific set of observations or experiments will be. Multiple hypotheses, once they are validated and modified and altered to fit the evidence eventually evolve into a cohesive scientific theory.

E: And Steve, this is where people sometimes get confused because they think of the word theory as hypothesis. They think, you know, "I have a theory behind that, I have some vague thoughts or ideas." But in the context of science you must understand that theory means something that's very different. It's very different from hypothesis.

S: That's right, and that distinction is important of course, because oftentimes creationists or people who deny a specific scientific theory will use the colloquial definition of theory which is more of a guess or hypothesis, to say "well, that's just a theory." However stating a scientific belief as a theory says nothing about how certain scientists are about its truth, about its validity. A theory in science may be so well established by the evidence that it is also a well-established scientific fact.

J: Like the theory of relativity.

S: That's correct. The theory of relativity, the plate tectonic theory, the heliocentric Solar System theory, the germ theory of infectious disease, the genetic theory of inheritance - these are all over-arching theories that are extremely well-established to the point that they can be treated as facts.

B: So theories are fashioned to explain a phenomenon that's happened in the natural world.

S: And not just a single phenomenon. Again usually they bring together multiple independent lines of evidence, multiple phenomenon. A good theory, a comprehensive theory will make many many predictions, not just one specific prediction.

M: In A Brief History of Time Steven Hawking wrote

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory.

B: One common misconception you may run across a lot is the notion that in science once you prove a theory it becomes a law. But theories are never promoted to laws. Science just doesn't work that way. Laws describe things, theories explain them. For example, the law of gravity says that if I drop a wrench on a planet with a positive gravity field, it falls. There is no attempt to explain why - that's the job of the theory of gravity. Newton did a decent job. Einstein's relativity does it even better, and now of course you can also apply this to evolution as well - the theory of evolution by natural selection is our best explanation for the fact of evolution.

J: Steve, so a scientist will spend his or her time developing a theory, which means coming up with predictions about a phenomena, a way to predict the result or the effect of a phenomenon?

S: That's actually more of a hypothesis, what you're describing. A theory is once you've established a certain number of phenomena and you're trying to explain them all with one underlying concept that brings them all together. Like if you take all of the different things that we've figured out about inheritance, like Mendel's pea experiments, he had a number of different experiments showing all sorts of different specific phenomenon about how color versus wrinkled and smoothness were inherited in peas, and then he had to develop an underlying theory of inheritance to explain all of these independent lines of evidence for all of these specific experiments that he was doing.

J: And when once the scientists develops the theory, at what point does he put it out for peer review or is that common with a theory?

S: Well, yes, of course, and it's actually probably in this day and age misleading to talk about a scientist doing that. You know, a hundred years ago, two hundred years ago it was more common for a single scientist to be working on their estate like Darwin or Newton, and develop a theory over many years and then publish a treatise in a book, but today it's much more common for multiple scientists to be working in a community effort, each publishing each little piece as they do it in the peer literature, sometimes even very preliminary ideas or preliminary research, discussing it at meetings, to the point where it's really a community effort. It's something that evolves over time in these little bits and pieces, so it's not generally the lone scientist working away in a lab, the image that is more based upon a quaint notion of what happens, you know, centuries ago.

Also one final word on another term, the term paradigm. A paradigm is actually a bigger concept than even a theory. The term was originally coined by Thomas Kuhn in his book The Structure of Scientific Revolutions. He used it to mean an overall way of looking at the world and a way of explaining things, almost like something that can be incorporate multiple theories within it. Although he was using the term to describe the process by which science changes over time, noting that a paradigm was an internal construct and then one internal construct would switch over, a shift from one paradigm to another. But there wasn't any necessarily external validity, although I think that those notions have been largely rejected by philosophers of science. The term paradigm has come into use again to still mean a general mode of explanation or of a way to approach how to think about or how to formulate theories to explain nature. So in a way it is actually hierarchically above a theory in terms of the way we would organize explanatory systems.

S: SGU 5x5 is a companion podcast to the Skeptics' Guide to the Universe, a weekly science podcast brought to you by the New England Skeptical Society in association with skepchick.org. For more information on this and other episodes, visit our website at www.theskepticsguide.org. Music is provided by Jake Wilson.