Varia

Prolongement d’une discussion estivale sur les inférences logiques avec le paradoxe de Caroll. Des deux propositions suivantes

• (A) Des choses qui sont égales à la même chose sont égales entre elles
• (B) Les 2 côtés de ce triangle sont des choses qui sont égales à la même chose

on doit conclure que

• (Z) Les 2 côtés de ce triangle sont égaux entre eux

Or, c’est que la Tortue refuse d’accorder à Achille^[1]. Elle est prête à accepter

• (C) si A et B sont vrais, Z doit être vrai
• (D) si A et B et C sont vrais, Z doit être vrai

mais elle refuse toujours d’admettre la conclusion (Z).

Comme l’écrit Pascal Engel

« peut être la Tortue veut-elle soulever un problème sceptique quant à l’application des règles logiques. En quoi le fait de reconnaître la règle du modus ponens comme une norme du raisonnement peut il être suffisant pour nous conduire à agir ? La Tortue n’est-elle pas victime d’une sorte d’akrasia inférentielle qui lui fait voir le meilleur (logiquement) mais lui fait suivre le pire ? Ou n‘est-elle pas, comme Lord Jim dans le domaine de l’action, victime d’une version cognitive de ce que les médiévaux appelaient accidie ^[2]? Qu’ai-je à faire de la logique, semble–t-elle dire. Comment ne pas lui donner raison ? J’ai connu un logicien, amant transi, qui s’attendait à ce que l’objet aimé effectue un modus ponens, mais était tout étonné que sa belle ne détache ni même ne contrapose. »

Quelle stratégie adopter face à ce refus de l’élève la Tortue ? C’est ce que vous pouvez découvrir dans les actes du séminaire Enseigner la philosophie, faire de la philosophie. En complément du texte précité sur la notion de démonstration (pp. 51-63), on pourra lire La rationalité des démonstrations de Pascal Ludwig (pp. 107-123).

« Turing was a quite brilliant mathematician, most famous for his work on breaking the German Enigma codes. It is no exaggeration to say that, without his outstanding contribution, the history of World War Two could well have been very different. He truly was one of those individuals we can point to whose unique contribution helped to turn the tide of war. The debt of gratitude he is owed makes it all the more horrifying, therefore, that he was treated so inhumanely. In 1952, he was convicted of gross indecency - in effect, tried for being gay. His sentence - and he was faced with the miserable choice of this or prison - was chemical castration by a series of injections of female hormones. He took his own life just two years later.

Thousands of people have come together to demand justice for Alan Turing and recognition of the appalling way he was treated. While Turing was dealt with under the law of the time and we can’t put the clock back, his treatment was of course utterly unfair and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him. Alan and the many thousands of other gay men who were convicted as he was convicted under homophobic laws were treated terribly. Over the years millions more lived in fear of conviction.

I am proud that those days are gone and that in the last 12 years this government has done so much to make life fairer and more equal for our LGBT community. This recognition of Alan’s status as one of Britain’s most famous victims of homophobia is another step towards equality and long overdue.

But even more than that, Alan deserves recognition for his contribution to humankind. For those of us born after 1945, into a Europe which is united, democratic and at peace, it is hard to imagine that our continent was once the theatre of mankind’s darkest hour. It is difficult to believe that in living memory, people could become so consumed by hate - by anti-Semitism, by homophobia, by xenophobia and other murderous prejudices - that the gas chambers and crematoria became a piece of the European landscape as surely as the galleries and universities and concert halls which had marked out the European civilisation for hundreds of years. It is thanks to men and women who were totally committed to fighting fascism, people like Alan Turing, that the horrors of the Holocaust and of total war are part of Europe’s history and not Europe’s present.

So on behalf of the British government, and all those who live freely thanks to Alan’s work I am very proud to say: we’re sorry, you deserved so much better. »

Gordon Brown