You can't prove a negative. So what?

When confronted with a study that fails to find a clinically useful effect for a complementary and alternative medicine (CAM) therapy, advocates will often deny the importance of the evidence by saying You can't prove a negative?


So what? This misses the point.

The point of a clinical trial is to measure if a treatment has a clinically useful effect. It is not to prove a basic law of nature, or the existence or non-existence of anything?

If trials find that a treatment does not have a clinically useful effect, and the risk of bias and error in the results is small, then there is no point in doing more research that is likely to find the same negative results.