(This is the English version of my article on 22th/11/2020. この記事は下記の英語訳になります。)
「物事が起こる理由が、一つだけだと誰が決めた？」 - ともいしろの雑記帳 (hatenablog.com)
This is something that happens all the time in research, or even in the treatise I'm reading now. When a certain result is derived or expected from a certain cause, could you be convinced by hearing only one reason? If yes, it's very dangerous.
As an example, think the question "Is wearing a mask effective in preventing virus-related diseases?" It's a topic I've touched on often before.
Now, let's assume that I insist "masks are NOT effective against viruses!", and the reason is "The size of the virus is much smaller than the mesh of the mask → The virus can almost pass through and enter into the body." If so, would you be convinced? The knowledge of the size of the virus is correct. Still, I don't think many people are persuaded.
To certify that "Wearing a mask can be the reason of less susceptible to viral diseases", there can be several ideas.
(1) Physically shut out the virus (this is denied above).
(2) The mask causes water vapor to accumulate inside the mouth an nose, which weakens the virus.
(3) The mask cannot repel viruses, but can prevent other large bacteria and dust. As a result, the waste of physical strength and immunity that originally dealt with these small fish enemies has disappeared. You will be able to concentrate on fighting off the virus.
(4) Due to the sense of security of "wearing a mask" and the psychosomatic correlation, the body and immunity are kept healthier than when not wearing it. It's almost a mental theory.
If you really want to insist that "masks are meaningless!", you have to eliminate all these reasons. To put it the other way around, it is not possible to determine which of the above reasons is responsible for the statistical results that "masks are valid". Similarly, if a scientific paper only "discovers" a new causal relationship but does not "elucidate" the reasons, the rating will be one step lower (although it will not be zero).
Also, as a meta-analytic story, there is such a possibility.
(5) Many people who are alert and wear masks also take self-defense measures (those that are truly effective in preventing viruses). As a result, mask wearers are less susceptible to the virus.
Personally, I haven't been able to affirm or deny all of these issues on my own, so the judgment that "Mask is bla bla bla ..." is pending.
However, humans often want a single path from cause to effect. Because it's easier. Simple and clear treatises and explanations are more popular and reassure you. It may be the true value of intellectuals to be able to resist this temptation and investigate various possibilities.
But, well, that's also a problem if you just claim a too difficult order and throw it as "a possibility to be verified!".