Using Google Books’ Ngram, I traced the battle between “mind” and “body,” “heart” and “soul” in literary history. Does anybody have an idea of what might account for that major spike in “heart” in the late-17th century? I then graphed the occurrence of friends and enemies in literature since the 1600s. Note the not-so-coincidental points where “friend” and “enemy” are used equally, or usage of “enemy” exceeds usage of “friend.”If you haven’t checked out Google Books’ Ngram feature yet, you’re in for a treat. Ngram searches Google’s enormous database of books to give a visualization of word usage over time. Of course, word usage shouldn’t be mistaken as an accurate barometer of the zeitgeist of different periods so much as an indication of what those who were writing were writing about, and it’s obvious that some of the words I’ve chosen – such as “mind,” which was probably used as a verb as often as a noun – can’t actually gauge the frequency with which they were used in a particular context. Still, fascinating!