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.
Apocolpse probably needs something stronger like distilling skills.
Or how to make edibles.
Distillation alone would be useful for disinfection and conservation.
I can do those too! Hooray, I’m valuable
We value you regardless, guazzabuglio.
Appreciate it