Except for the fact that nothing in the content of the article explains the preposterous title of **Known Unknowables** (*if a thing is unknowable how can one know about it?*) the article is an excellent read about the evolution of #skepticism or what #Maturana calls ***Objectivity in Parentheses***.
https://aeon.co/essays/four-scepticisms-what-we-can-know-about-what-we-cant-know