3 3 6 D O C U M E N T 2 2 0 R E S P O N S E T O B O V E T Published in Wissen und Leben 15 (1922): 902. A handwritten [25 037] and a typed [25 038] version are also available. [1]Bovet (1870–1941) was Professor of French and Italian Literature at the University of Zurich, founder and director of the journal Wissen und Leben, and secretary of the Schweizerische Völkerbundliga. [2]In May 1922, Paul Langevin had delivered three lectures on relativity in Zurich, the first of which was addressed to a general audience and was a great success. In reaction to Langevin’s lectures and their enthusiastic reception, Bovet published an open letter to Langevin. In it, Bovet admits that, during his studies thirty years earlier, he had only attended a general lecture in physics and mathemat- ics. Nevertheless, he found Langevin’s lecture interesting and was especially surprised by the frenetic applause that it drew from scholars and laymen alike. This raised in him the “psychological” question as to the reasons for this enthusiasm. Sketching his own understanding of the history of science, Bovet posed the questions: “What is the relationship between the theory of relativity and the social ethics absolutely necessary for the reconstruction of a civilization? […] To what extent are we liberated from rational mechanics?” (“Quel rapport y a-t-il entre la théorie de la relativité et la morale sociale dont nous avons absolument besoin pour reconstruire une civilisation? […] En quelle mesure sommes- nous libères de la mécanique rationelle?” Bovet 1922, p. 648). Langevin did not reply. But Bovet received and published responses by both Einstein and Hermann Weyl. (For an English translation of their replies and historical commentary, see Weyl 2009, pp. 5–6, 25–28.) [3]“The order and connection of ideas is the same as the order and connection of things” (“Ordo et connexio idearum idem est ac ordo et connexio rerum” Ethica, Propositio VII, Pars 2). Einstein had read Spinoza’s Ethics in July 1917 (see his letters to Elsa Einstein, 3 and 6 July 1917 [Vol. 8, Doc. 115, and Vol. 8, Doc. 359c, in Vol. 10]). In the autograph version, the words “bezw. Fechner” are interlineated. [4]In Bovet 1922, Bovet quotes from Poincaré 1902 and 1905 the sentences: “Axioms are nothing more than disguised definitions” (“Les axiomes ne sont que des définitions déguisées”) and “The sci- entist must classify one practices science with facts the way one builds houses with stones but an accumulation of facts is no more a science than a pile of stones is a house” (“Le savant doit ordonner on fait la science avec des faits comme une maison avec des pierres mais une accumulation de faits n’est pas plus une science qu’un tas de pierres n’est une maison”). He also wrote: “In 1898, Henri Poincaré wrote: ‘In fine, it is our mind that furnishes a category for nature. But this category is not a bed of Procrustes into which we violently force nature, mutilating her as our needs require. We offer to nature a choice of beds among which we choose the couch best suited to her stature” (“En 1898 Henri Poincaré écrivait: «En résumé, c’est notre esprit qui fournit une catégorie à la nature. Mais cette catégorie (la géométrie) n’est pas un lit de Procruste dans lequel nous contraignons violemment la nature, en la mutilant selon que l’exigent nos besoins. Nous offrons á la nature un choix de lits parmi lesquels nous choisissons la couche qui va le mieux á sa taille»”). The reference Bovet gives is to Poincaré 1921, a French translation of a text that first appeared in English as Poincaré 1898. The quoted passage is the concluding paragraph of that work (Poincaré 1921, p. 64, or Poincaré 1898, p. 43, respectively). [5]“Later, in conversation with a distinguished professor of mechanics who was one of your audi- tors on Monday, 22 May, and reverting to my fetishist respect for the ‘exact’ sciences, I told him: ‘How lucky you are to practice a science that leads to certainties!’ to which he responded: ‘Indeed, mechanics explains everything in the world there is only one question to which it does not provide an answer: what is the purpose of the human spirit? That’s the only question that interests me.’— This melancholy phrase is one of the greatest gifts that I received in my life. “‘What is the purpose of the human spirit?’ Of course I do not ask that you answer this question which looms like a giant ax on the horizon of all human thought, but I would like to know whether the new mechanics opens up any modest hope to possibilities of a different sort?” (“Plus tard, conver- sant avec une illustre professeur de mécanique, qui fut un des vos auditeurs le lundi 22 mai, et retom- bant dans mon respect fétichiste des sciences «exactes,» je lui dis: «Comme vous êtes heureux de manier une science qui mène à des certitudes!» à quoi il répondit: «Certes, la mécanique explique tout