The example is of a simple case and how one would need to verify if someone or
something represents "facts" (I was neither focusing on the measuring error, so I should not have brought it up: my apologies).
> We can just say that the fact is that the speed meter reads 60.
(As an aside, my car needs software recalibration at the dealer if I switch to differently sized wheels: if I don't know to what wheel size software was calibrated to, I would need to verify it)
"Just say" is a manifestation of a "belief". The question is how do you, in a grand scheme of things, establish if it's not a "false belief"? You are, ultimately, putting your trust in somebody else doing the verification (of a speedometer in a car, in this example)!
Basically, it is our hope that actual facts will "surface" through this chain of trust between people into majority of people's heads, but throughout periods in history, that was not the case: eg. think Middle Ages; or any of the propaganda initiatives by the modern media.
As an obvious example of such a modern media play, I am sure you'd find most of the people in the USA before the Iraq invasion believed Iraq had been actively developing WMD. A quick search gives me this (I have no idea how trustworthy the source is, but such caveats should be assumed in human communication):
> Moreover, the share of the American public that believed it was “very likely” that U.S. forces would eventually uncover Iraqi weapons of mass destruction fell from 59 percent in early April to 39 percent in late April.
(From https://www.brookings.edu/articles/rally-round-the-flag-opin...)
As far as we know, at least 59% of Americans had "false beliefs" prior to the invasion, and even after troops were there, 39% still maintained them!
In accepting that it's too easy to have false beliefs promulgate, we open ourselves to an ability to develop tools and processes to combat that. But I truly wonder what are the practical tools we have to do that today? How is a "regular" Jane or Joe going to do that?