The title is a bit over dramatic but, per the title, if you could contribute with one piece of knowledge to a book that every single individual should learn from in order to kickstart a civilization, what would be yours?
My personal choice would be the process of soap making, from scratch.
Which philosopher/language are we talking about?
A philopher from an eastern country, pre USSR. I can’t recall the name; was made aware of the person in a YT rabbit hole. That tidbit stayed but the name vanished.