Not “just” a theory

In response to this blog post, Graydon wrote:

“To be a little nit-picky: there aren’t very many science *facts*. There are a lot of theories, and they are often very sound theories in that they hold true with observed historical data and they predict future observed data. Mr. Goodyear could have just said he didn’t believe in the theory of evolution, and that would have been one thing (admittedly not a great thing, evolution is a pretty widely trusted theory). But I agree, to link it to his religious beliefs has frightening implications that his religious beliefs affect his ability to make scientific decisions. That is to say: goodbye stem cell research in Canada?”

And he is correct. Most of scientific knowledge is composed of theories. However, there is a very big difference between the colloquial definition of theory and the scientific definition of theory.

Generally we understand theory to mean speculation or hypothesis. One cannot reach an evidence-based conclusion via a set of facts, so one posits a theory.

The following explanation of scientific theory is taken from the U.S. National Academy of Sciences book Science, Evolution, and Creationism:

“Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not ‘guesses’ but reliable accounts of the real world. The theory of biological evolution is more than ‘just a theory.’ It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.”

The following explanation of scientific theory is taken from the National Academies web site:

“The formal scientific definition of theory… refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Many scientific theories are so well established that no new evidence is likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics).

Like these other foundational scientific theories, the theory of evolution is supported by so many observations and confirming experiments that scientists are confident that the basic components of the theory will not be overturned by new evidence. However, like all scientific theories, the theory of evolution is subject to continuing refinement as new areas of science emerge or as new technologies enable observations and experiments that were not possible previously.

One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that have not yet been observed. For example, the theory of gravitation predicted the behaviour of objects on the moon and other planets long before the activities of spacecraft and astronauts confirmed them. The evolutionary biologists who discovered Tiktaalik [] predicted that they would find fossils intermediate between fish and limbed terrestrial animals in sediments that were about 375 million years old. Their discovery confirmed the prediction made on the basis of evolutionary theory. In turn, confirmation of a prediction increases confidence in that theory.

In science, a ‘fact’ typically refers to an observation, measurement, or other form of evidence that can be expected to occur the same way under similar circumstances.

However, scientists also use the term ‘fact’ to refer to a scientific explanation that has been tested and confirmed so many times that there is no longer a compelling reason to keep testing it or looking for additional examples. In that respect, the past and continuing occurrence of evolution is a scientific fact. [Emphasis mine.]

Science depends wholly on empirical evidence and testable explanations that have been overwhelmingly substantiated. All accepted scientific knowledge has withstood extensive testing and retesting by various scientists across the world and over time. Evolution, for example, has been tested by thousands of scientists for 150 years.

Creationists or intelligent design proponents (“neo-creationists”) count on the public’s ignorance of the definition of scientific theory when they say things like, “Evolution is just a theory.” Yes, and so are gravity, the theory of relativity, germ theory, the genetic basis of heredity, and the circulation of blood. All just theories. In truth, they are factual descriptions of the natural world accepted by scientists.

Anti-evolutionists will also claim that there is still disagreement within the scientific community about evolution. This is a half-truth. Scientists do not question whether evolution is true, but they still debate the mechanisms by which it works. As always takes place in science, scientists continue to study how things work after they have concluded that they do work (see above example of gravity).

Again from the National Academies:

“Because the evidence supporting it is so strong, scientists no longer question whether biological evolution has occurred and is continuing to occur. Instead, they investigate the mechanisms of evolution, how rapidly evolution can take place, and related questions.”

Don’t be entangled by those who would try to fool you with semantics. Scientific theory or more than “just a theory.”

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One CommentLeave a comment

  1. i think popular culture does little to help rectify this sort of semantic confusion. in tv shows that are presented as “scientific” (from csi to star trek to house) characters often bounce around theories and say things like “theoretically it’s possible…”, which only serves to obfuscate the scientific use of the word: theory.

    it’s easy for people to forget that real forensic scientists, doctors, and physicists very often find those shows laughable in their pseudo-science. macgyver — now that’s science!

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