A brilliant Facebook post by Kaj Sotala. Posted partly so I can link people here when I need to tell them there’s no scientific evidence for something:
One of the biggest ways by which scientists and science-minded people fail to communicate with laypeople, I think, is with the phrase “there’s no scientific evidence for X”.
Suppose that a layperson comes to a scientist and explains excitedly that he just heard of a new way to [raise children/lose weight/cure illnesses] that works great, and everyone should adopt that method at once!
The scientist replies that she has heard of that method too, but so far there’s no scientific evidence for it.
By that, the scientist means something roughly like “Well, there might be something to it, but the successes that you mention could very well just be coincidence, and it’s really really hard to figure out whether that thing actually works, even if we do lots of careful experiments. So although the thing that you mention could be worth looking into, we really don’t know whether it works yet, and most things like that actually turn out not to work when you do the experiments, so for now we should assume that it won’t work.”