Karl Jaspers: the forgotten father of existentialism
aeon.co
aeon.co
He's also known as the mentor of Hannah Arendt, who later wrote "Origins of Totalitarianism", "The Human Condition" (Alan Kay's favorite book[1]) and "Eichmann in Jerusalem" (served as basis of her 2012 biopic[2])
[0] https://www.amazon.com/dp/1590514882
[1] http://www.squeakland.org/resources/books/readingList.jsp