In response to
A few words about shorthand arguments
"Somebody would have noticed" is shorthand for a certain argument. Like most shorthand arguments, it can be used well or badly. Using a shorthand argument badly is what we mean by a "fallacy".
A shorthand argument is used well, in my opinion, just if you could expand it to the longhand form and it would still work. That's not a requirement to always do the full expansion. You don't have to expand it each time, nor have 100% confidence of success, nor expand the whole thing if it's long or boring. But expanding it has to be a real option.
A list of salient critical questions
Critical questions that arise in expanding this particular argument:
What constitutes noticing?
- Would other people who noticed understand what they saw?
Further, would they understand it the same way that we do?
- How much potential is there for their understanding of the same phenomenon to be quite different from ours?
Further, if their understanding is similar to ours, would they
express it in terms that we would recognize?
- This could include actions that we recognize as relating to the phenomenon.
Would we know that they noticed?
Motivations: Would people who noticed have strong motivations for
letting others know or for not letting others know?
- Would they want others to see that they noticed?
- Would they want others to see the phenomenon they noticed?
- Would they want to do something about it that someone could easily see?
- If they did want others to know, could they easily show it?
- Conversely, if they didn't, could they easily hide it?
Who witnesses it:
- Would they want us in particular to see it (or not see it), as opposed to a select group? For instance, they might write a report about it that you and I probably wouldn't see.
- If they revealed it to others but not directly to us, what's the likelihood that the information would make its way to us?
- Motivations: Would people who noticed have strong motivations for letting others know or for not letting others know?
The suppressed premise in that emthymeme is that "Nobody noticed".
Since we didn't ask everyone in the world, how did we determine
- What is the population that would have noticed?
- What sample size did we take?
- How representative was our sampling?
- Assuming we have reasonable answers to the above, what level of confidence can we place on our sampling?