"Larvatus prodeo," announced René Descartes at the beginning of the seventeenth century: «I come forward, masked.» Deliberately disguising or silencing their most intimate thoughts and emotions, many early modern Europeans besides Descartes-princes, courtiers, aristocrats and commoners alike-chose to practice the shadowy art of dissimulation. For men and women who could not risk revealing their inner lives to those around them, this art of incommunicativity was crucial, both personally and...