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Proof vs. Evidence June 19, 2007

Posted by Joe in belief, creationism, evolution, fallacy, freethought, logic, psychology, science.

The Hovind challenge referenced yesterday repeatedly called for “scientific proof” of evolution. There is no proof in science. Proof is for mathematics and alcohol. You cannot prove anything in science to a certainty, though you can disprove a lot. All scientific theories are tentative and subject to revision. Even the “law of” gravity is subject to revision, and in fact was revised by Einstein’s general theory of relativity.

Science is about evidence. Evidence is the result of a structured scientific experiment or observation that supports the claims of a theory. In order to be useful a different outcome for the experiment or observation must be able to falsify or disprove the theory.

That is, there must be a well defined result that if observed would demonstrate that the theory would be false. Every experiment or observation must be structured to test the theory, thus allowing the possibility for it to fail. A theory can be disproved by a single verifiable counter-example, but no amount of confirming evidence can ever demonstrate a theory to 100% certainty.



1. Ed Yong - June 19, 2007

“Proof is for mathematics and alcohol.” Lovely.

The situation is really not helped by sloppy headlines/press releases which proclaim “Scientists find proof of something or other” or “It’s official – bananas cause strokes”

2. Joe - June 19, 2007

Yes, and it is even worse that most of those headlines are reporting the findings of a single study, and rarely mention the difference between correlation and causation.

3. Richard Wade - June 23, 2007

The difference between correlation and causation is difficult to explain and difficult at first to grasp for the scientifically uninitiated. It also helps to have at least an IQ of 100. That makes it even more challenging for 50% of the population. Simple-minded people like things cut and dry, either/or. When they hear scientists talk about probabilities rather than proof they think they’re hedging or being evasive. The media often doesn’t help matters. When one crackpot scientist disagrees with the presiding theory, the newspapers call it a big controversy and give him at least half of the coverage. Having little or no evidence doesn’t seem to matter.

In my work I have to explain such things to lay people almost daily. Sometimes analogies help. For instance for correlation/causation I say that countries that have higher stork populations tend to have higher human birth rates. So those two factors correlate. But storks don’t bring babies. When the look of comprehension lights up their face I know I’ve succeeded. Otherwise I’ll try some other way.

4. Joe - June 25, 2007

It is a subtle distinction, but it is also a rather simple idea that should be taught to kids in grade school using real life examples.

If you don’t mind my asking, what do you do Richard?

5. religionandatheism - July 9, 2007

Here’s another subtle distinction: a counter-example falsifies the composite theory. That is, the theory as it stands in its entirety. Some counter-examples found by experiment may lead to the modification of a theory, rather than its total rejection.

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