Thing is, I think our brains effectively run on epistemological relativism -- it describes the map the brain builds about the world outside -- but "objective reality" indirectly measured via action and reaction is what keeps it honest.
You might believe you're the leader of your country, and you are as long as everybody else also thinks you're the leader - and as soon as they stop believing it, it's no longer true. This is shared, constructed reality in action, and it's also "objectively true": if you imagined a disinterested observer looking at a human society through a set of powerful instruments, they could identify you as the leader. It still doesn't stop you coming down to earth with a bump if you believe you can fly, of course.
> but "objective reality" indirectly measured via action and reaction is what keeps it honest.
Which is great when you're talking about stuff you can poke and kick and study but people very quickly start creating new stuff like "beauty" and "justice" and all the other nouns that you can't kick or poke.
Even things you can kick or poke start to become rather tricksy if you're not careful:
It's not unreasonable to argue that the number of things that are amenable to uncontroversial objective study is rather small. We live in a world full of nouns and we aren't terrible clear on which ones are objective and which ones aren't.
You might believe you're the leader of your country, and you are as long as everybody else also thinks you're the leader - and as soon as they stop believing it, it's no longer true. This is shared, constructed reality in action, and it's also "objectively true": if you imagined a disinterested observer looking at a human society through a set of powerful instruments, they could identify you as the leader. It still doesn't stop you coming down to earth with a bump if you believe you can fly, of course.