Free Speech: A History From Socrates to Social Media, by Jacob Mchangama, Basic Books, 528 pages, $32
Many languages have in-built speech codes: There are levels of formality and informality in address, words that are not to be used in certain contexts, even forms of speech specific to men and women. European languages tend not to carry the levels of baroque distinction found elsewhere, but they still maintain formal and informal registers. English is distinctive in having essentially abandoned them; our you was once the formal/plural form of address (thee being the familiar).
