I recall (maybe incorrectly) a story about a mathematician trying to be a tutor to some nobleman (French, i think). Nobleman got impatient with the intricacies of mathematical proof and asked "Why do you bother with this stuff?" Tutor said "so you will know for sure that what I say is true." Nobleman said "If that is the point, this is all unnecessary--i would not dream of doubting your word."
Who were the nobleman and tutor? and what's the source? or am i hallucinating this story?
thanks
It's almost surely "Le bourgeois gentilhomme", one of the foremost play of Molière (1670).
It is not a gentleman (gentilhomme) but a snobbish wealthy man (bourgeois) who hires private teachers in order to acquire "good manners" in different domains: dance, litterature, philosophy (here, its aristotelian logic component)...
The integral text can be found here. The part you mention is in pages 13-14.
I don't know if you are fluent in French ; I have given a translation below.
MAÎTRE DE PHILOSOPHIE, en raccommodant son collet.— Venons à notre leçon.
MONSIEUR JOURDAIN.— Ah! Monsieur, je suis fâché des coups qu'ils vous ont donnés.
MAÎTRE DE PHILOSOPHIE.— Cela n'est rien. Un philosophe sait recevoir comme il faut les choses, et je vais composer contre eux une satire du style de Juvénal, qui les déchirera de la belle façon. Laissons cela. Que voulez-vous apprendre?
MONSIEUR JOURDAIN.— Tout ce que je pourrai, car j'ai toutes les envies du monde d'être savant, et j'enrage que mon père et ma mère ne m'aient pas fait bien étudier dans toutes les sciences, quand j'étais jeune.
MAÎTRE DE PHILOSOPHIE.— Ce sentiment est raisonnable, Nam sine doctrina vita est quasi mortis imago. Vous entendez cela, et vous savez le latin sans doute.
MONSIEUR JOURDAIN.— Oui, mais faites comme si je ne le savais pas. Expliquez-moi ce que cela veut dire.
MAÎTRE DE PHILOSOPHIE.— Cela veut dire que sans la science, la vie est presque une image de la mort.
MONSIEUR JOURDAIN.— Ce latin-là a raison.
MAÎTRE DE PHILOSOPHIE.— N'avez-vous point quelques principes, quelques commencements des sciences?
MONSIEUR JOURDAIN.— Oh oui, je sais lire et écrire.
MAÎTRE DE PHILOSOPHIE.— Par où vous plaît-il que nous commencions? Voulez-vous que je vous apprenne la logique?
MONSIEUR JOURDAIN.— Qu'est-ce que c'est que cette logique?
MAÎTRE DE PHILOSOPHIE.— C'est elle qui enseigne les trois opérations de l'esprit.
MONSIEUR JOURDAIN.— Qui sont-elles, ces trois opérations de l'esprit?
MAÎTRE DE PHILOSOPHIE.— La première, la seconde, et la troisième. La première est, de bien concevoir par le moyen des universaux. La seconde, de bien juger par le moyen des catégories: et la troisième, de bien tirer une conséquence par le moyen des figures. Barbara, celarent, darii, ferio, baralipton, (see (*)) etc.
MONSIEUR JOURDAIN.— Voilà des mots qui sont trop rébarbatifs. Cette logique-là ne me revient point. Apprenons autre chose qui soit plus joli.
Translation (Adapted from an initial one, rather accurate, from Google Translate):
MASTER OF PHILOSOPHY. (mending his collar) Let us come to our lesson.
MONSIEUR JOURDAIN. Oh! Sir, I am sorry for the blows they gave you.
MASTER OF PHILOSOPHY. That is nothing. A philosopher knows how to receive things properly, and I am going to compose a satire in the style of Juvenal against them, which will tear them apart in a beautiful way. Let’s leave that. What do you want to learn?
MONSIEUR JOURDAIN. All that I can, for what I desire the most in the world is to be a scholar, and I am enraged that my father and my mother did not make me study well all sciences, when I was young.
MASTER OF PHILOSOPHY. This feeling is understandable, Nam sine doctrina vita est quasi mortis imago. You hear that, and you probably know Latin.
MONSIEUR JOURDAIN. Yes, but pretend I don't know. Explain to me what that means.
MASTER OF PHILOSOPHY. This means that without science, life is almost an image of death.
MONSIEUR JOURDAIN. That Latin is right.
MASTER OF PHILOSOPHY. Have you been introduced to some principles, some bits of science?
MONSIEUR JOURDAIN. Oh yes, I can read and write.
MASTER OF PHILOSOPHY. Where would you like us to start? Do you want me to teach you logic?
MONSIEUR JOURDAIN. What is this logic?
MASTER OF PHILOSOPHY. It teaches the three operations of the mind.
MONSIEUR JOURDAIN. Who are these three operations of the mind?
MASTER OF PHILOSOPHY. The first, the second, and the third. The first is to conceive properly by means of universals. The second, to judge well by means of categories: and the third, to draw proper consequences by means of figures: Barbara, celarent, darii, ferio, baralipton, (see (*)) etc.
MONSIEUR JOURDAIN. These are words that are too off-putting. This logic does not appeal to me. Let's learn something else that is prettier.
(*) Personal note: these pseudo-latin words were mnemonics helping students to remember the main correct ways to construct syllogisms ; for example the voyels in "barbara", i.e., A A A, translated into our modern quantifiers meant $\forall$ and $\forall$, then $\forall$, for example:
All cats are felines, all felines are mammals, then all cats are mammals.