1. Biography

Jules Henri Poincaré was born on 29 April 1854 in Nancy in the Lorraine region of France. His father was professor of hygiene in the School of Medicine at the University of Nancy. His cousin Raymond was to become the President of the Republic of France during the period 1913–1920 and his younger sister Aline married the philosopher Émile Boutroux. Henri was a precocious student who rose immediately to the top of his class, excelling in both science and lettres . At age 13, his teacher told his mother that “Henri will become a mathematician … I would say a great mathematician” (Bellivier 1956: 78). During the Franco-Prussian war in 1870 the Germans occupied Nancy and the Poincaré family was obliged to billet the secretary of the civil commissar of Nancy, with whom Henri would have a round of conversation each night after dinner in order to improve his German (see Boutroux 2012).

In 1871 Poincaré passed the exams in lettres with the grade “good” and that in science with the grade “fair”.…