It’s a tribute to John Venn, the diagram’s creator, born today in 1834. (Incidentally, I disagree with the linked Guardian piece’s assertion that the doctor/prostitute/TSA diagram is ...

British mathematician John Venn (pictured above, click to enlarge) was born on August 4, 1834, so tomorrow will mark the 187th anniversary of his birth in Hull, England. John Venn is most known ...