Miriam Ruiz
random thoughts on technology and life

{May 25, 2007}   3rd anniversary of Debian Women

It’s 3 years since Debian-Women’s mailing list was created. Time for celebration!

{May 25, 2007}   What’s a Theory? What’s an Hypothesis?

Evolution, then, is a theory, one of the most influential, farreaching and important theories ever devised. In this context, it’s worth pointing out that the word `theory’ is often used in a quite different sense, to mean an idea that is proposed in order to be tested. Strictly speaking, the word that should be used here is `hypothesis’, but that’s such a fussy, pedantic-sounding word that people tend to avoid it. Even scientists, who should know better. `I have a theory,’ they say. No, you have a hypothesis. It will take years, possibly centuries, of stringent tests, to turn it into a theory.

The theory of evolution was once a hypothesis. Now it is a theory. Detractors seize on the word and forget its dual use. `Only a theory,’ they say dismissively. But a true theory cannot be so easily dismissed, because it has survived so much rigorous testing. In this respect there is far more reason to take the theory of evolution seriously than any explanation of life that depends on, say, religious faith, because falsification is not high on the religious agenda. Theories, in that sense, are the best established, most credible parts of science. They are, by and large, considerably more credible than most other products of the human mind. So what these people are thinking of when they chant their dismissive slogan should actually be `only a hypothesis’.

That was a defensible position in the early days of the theory of evolution, but today it is merely ignorant. If anything can be a fact, evolution is. It may have to be inferred from clues deposited in the rocks, and more recently by comparing the DNA codes of different creatures, rather than being seen directly with the naked eye in real time, but you don’t need an eyewitness account to make logical deductions from evidence. The evidence, from several independent sources (such as fossils and DNA), is overwhelming. Evolution has been established so firmly that our planet makes no sense at all without it. Living creatures can, and do, change over time. The fossil record shows that they have changed substantially over long periods of time, to the extent that entirely new species have arisen. Smaller changes can be observed today, over periods as short as a year, or mere days in bacteria.

Evolution happens.

What remains open to dispute, especially among scientists, is how evolution happens. Scientific theories themselves evolve, adapting to fit new observations, new discoveries, and new interpretations of old discoveries. Theories are not carved in tablets of stone. The greatest strength of science is that when faced with sufficient evidence, scientists change their minds. Not all of them, for scientists are human and have the same failings as the rest of us, but enough of them to allow science to improve.

The Science of Discworld III: Darwin’s Watch

by Terry Pratchett, Ian Stewart and Jack Cohen


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