By Sarah Bakewell, Other Press, New York, N.Y. 400 pages, $25

Ours is an age when revealing facts about one’s personal life has become commonplace. There is no shortage of blogs on the Web or reality TV shows where the authors or stars are happy to share the most intimate details with whomever clicks on the blog or turns on the television. It is fascinating to consider that the origin of these tell-all narratives may be a 16th-century French philosopher.