Welcome back to "Doggerel," where I ramble on about words and phrases that are misused, abused, or just plain meaningless.
There are a fair number of woos out there who will claim that their woo powers have very obvious effects, and yet when confronted and asked to produce them, they will often shift to claim that they're "subtle," as if that were a barrier to scientific investigation.
The more subtle the effect, the more you have to rely on tight protocols or, in other words, science. Despite woos trying to claim the invisible for themselves, it is science that has brought us knowledge of invisible things we now take for granted in our everyday lives.
Usually, woos claim that whatever they believe in has effects, but retreat into this doggerel when those effects fail to show up, or if there's lots of unmonitored confounding factors to deal with. Controlled experiments are designed to eliminate or reduce confounding factors. If the effects don't show up, isn't it much simpler to conclude they don't exist? All "subtle" does is increase the number of trials, require slightly more precise equipment, and that sort of thing. The question then becomes: If it's that subtle, what makes you think it exists in the first place?