There is never no evidence (part 1)

posted by Carl V Phillips

I just finished submitting some testimony on another matter where this topic came up, and I thought I would expand upon it for a few posts while I am thinking about it.  Rather than identifying any specific liar or statement, this is a generic debunking of any claim that there is no evidence that allows us to assess the answer to a question.  This is what is being claimed by anti-THR liars when they say something like “there is no evidence that e-cigarettes pose lower risk than smoking” or “there is no evidence that low-risk alternatives help people to quit smoking”.

There are legitimate uses of the phrase “no evidence”, such as “having evaluated the available evidence, I have seen no evidence that advising people that snus is a low-risk alternative to smoking causes anyone to start smoking.”  But when anti-THR activists use the phrase “no evidence” they saying “there is no evidence to evaluate” not “the evidence that exists does not support this claim” (if there are any exceptions to this usage by them, I have not noticed them).

It is obvious why they want to do this:  The evidence has a strongly pro-THR bias, so they would prefer to say that it does not exist.  But it is also obvious that when they do this they are lying.  That is (in keeping with the use of term in this blog) they are either saying something they know to be false, or they are claiming to understand science and are making assertions about it, but they really do not know what they are talking about, and so are lying in their implicit claim that they are qualified to be making subject matter claims (or, to put it more bluntly, that they have a clue what they are talking about).

These particular lies, unlike some of the claims about toxic chemicals and such, probably skew more toward the latter type than the former.  That is, most of the people making these claims seem to have no understanding of how science works and what constitutes evidence, and so their lie is not so much that they know what they are saying is false, and more that they are claiming to know what they are talking about when they really do not.

Scientific inference is a process of drawing conclusions about some question of interest based on all available information.  High school debate contests and other stylized games may have specific rules about what constitutes allowable evidence, but science does not. Science makes use of whatever information is available (in addition to trying to create more information, of course).  So anytime someone claims that we do not know anything because we do not have a particular type of study result available, either they are lying or they are clueless about science.

To further motivate this point, consider three collections of evidence and conclusions based upon them (the first is real, the other two are stylized but I suspect one could find real studies that were quite similar with only a bit of searching)

Thousands of people living near electric generating wind turbines have reported experiencing a particular pattern of serious health problems that began when the turbines started operating.  A large portion of those reports describe how the problems abate when someone spends days away from home and reverse when they move away.  The conclusion is that the wind turbines are causing the health problems.

A group of a hundred overweight volunteers were randomized into one group that was given standard weight-loss advice and a second group that was assigned to eat a vegan diet.  At the end of two months, the vegan group had lost statistically significantly more weight on average.  The conclusion is that adopting a vegan dies is more effective than standard weight-loss techniques.

A large dataset with information on health and behavior was analyzed to estimate the health effects of television viewing.  After controlling for other behaviors, including alcohol consumption, those who watched more than 4.5 hours per day of television had a RR of 1.7 (95% CI 1.1, 2.6) for serious liver disease compared to those who watched less than 0.5 hours.  The conclusion is that watching television causes liver disease.

Which of these conclusions seem compelling, and why?

In the next part, I will assess that and relate the examples back to specific anti-THR lies (and explain a bit more about them for those who might not understand what all the jargon means).

…continued…