Wednesday, February 16, 2011

Scientific proof

I’ve been arguing with Maria here about scientific vs mathematical proof. It’s a distinction I think a lot of people get wrong and it can be harmful.  As I claim in the comments, it’s exactly the error creationists exploit when they say evolution is only a theory. It’s also made us unduly timid about making scientific claims. For example it’s made us believe that agnosticism is the only logically defensible position on religion. It’s made us feel that scientific proof is somehow weaker than mathematical proof and – worse – that this is a weakness of science.

I want to try to explain why this isn’t true.

Mathematical and scientific proofs differ because scientific proofs are based on empirical facts.  This makes them provisional.  New evidence could always conceivably overturn what we know now. But this doesn’t mean we can’t be 100% certain of something based on what we know now.  It doesn’t mean that our scientific proofs are weaker than our mathematical ones. 

For example, we can be 100% certain that evolution is true because of the enormous number of interlocking pieces of evidence.  We can be 100% certain even though we know that it’s technically possible (though astoundingly unlikely) that new evidence will appear which forces us to change our minds. 

Confusing scientific and mathematical proofs is a category error which I think has led us to be far too cautious about saying when something is true. It’s become fashionable to emphasise the perceived (but not actual!) weakness of the provisional nature of science, almost apologetically.  Instead, we should be applauding the strength of the scientific method in the face of provisional data.  It has triumphed at incorporating new evidence and sifting out bad conclusions.  Let’s stop apologising for the nature of the universe and acting as though it’s science’s fault!

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