Thursday, 2 September 2010

Common Sense and the Common Cold

In his book "Do they think you're stupid" Julian Baggini takes Edzard Ernst to task over something he said about homeopathy.
"If you study medicine and pharmacology, you know that [homeopathy] can't work" - Edzard Ernst
'The alternative professor' Sarah Boseley Guardian 25th Sept 2003.

Baggini says that this is an example of the fallacy that if there is no rational explanation then it cannot be true. He then gives the example of Lord Kelvin saying that heavier than air flying machines were not possible, to show how our knowledge of the world changes and that just because there is no rational explanation today, this does not mean that there will not be one tomorrow.

Now this is true to a certain extent, but truth is a rather deceptive and tantalising (in the historical meaning of the word) concept. There are some things we know and we can know that our models will not be supplanted by some alternatives - flat Earthers are not credible any more. Kelvin is actually not a very good example as he was actually wrong pretty often - he showed the world could not be ancient or the core would have cooled completely and so gave the creationists plenty of ammunution against Darwin. He also said at the end of the 19th Century there were only two clouds (problems to be solved) before physics would be complete. Sadly the clouds lead to relativity and quantum mechanics and the end of his view of physics. In the case of heavier than air flying machines he just had to look at birds - they are a bit heavier than air.  Anyway too much digression back to Ernst. What Ernst means is that if you know medicine and pharmacology you know that there is no mechanism that can possibly allow homeopathy to have an effect. So you do not need to carry out the experiments as Baggini suggests. As these are harder to carry out unequivocally to deal with the placebo effect.

Anyway a much bigger mistake is his dealing with common sense and why it is often wrong. His example is the common cold and he cites Lewis Wolpert who uses the example of your mum telling you to wrap up properly and to dry yourself properly or you will get a cold. I know of doctors who share my mum's view, although my brother spent most of his youth trying to show she was wrong. The common cold is a virus and so being damp or cold has no effect, but being inside keeping warm with virus carriers does (this is why we get more colds in winter). Baggini cites this as true but this is the exact same mistake that Ernst made. Has anyone done the experiment to see whether it is true? In this case the virus is the mechanism for getting the cold but could we expand on this mechanism?

What are the effects of getting cold or of going about with wet hair and not dried properly?
  • Your body takes action to protect your temperature.
  • You shiver.
  • You get goose bumps.
Could any of these factors "cause" a cold?

Now I use cause in the broadest sense. Are any of these factors contributing to increase the likelihood of you getting the virus? Now I can make some thought models - I can do what Kelvin should have done. Here are some hypotheses:
  1. When I am cold my body has to warm me up by generating more internal heat and burning more fuel, this takes more oxygen and so I breath more deeply and more frequently increasing the chances of taking one of those viral particles into my lungs and so "causing" my cold.
  2. By using energy to keep warm I cannot use that energy in my defence mechanisms such as my immune system which is constantly fighting the ever present virus. So as I get "run down" in my weakened state it is more likely that I get a cold.
  3. Colds and flu are more frequent in the winter months and we do not change our patterns of behaviour sufficiently to explain this difference just because of being indoors more, and so this correlation must hide a true causative effect that we have not discovered yet.
Now all of these are reasonable arguments that could be true - so maybe common sense should not be discounted in this case.

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