Raymond Smullyan R.I.P.

165Logiker Raymond Smullyan ist im stolzen Alter von 97 Jahren gestorben.

Der Mann war neben seinen mathematischen und philosophischen Arbeiten vor allem für seine populärwissenschaftlichen Bücher voller Rätsel und Puzzle bekannt. Sein Logik-Ritter und andere Schurken (engl. What Is the Name of This Book?) stand als Kind bei mir im Regal, hat aber nix genutzt, ich bin ’ne furchtbare Null bei Logik-Rätseln.

Iconic American mathematician, logician and puzzle-maker Raymond Smullyan has died at the age of 97.

News of his death was announced by his step-niece Alison Fleming, who said: "Uncle Raymond Smullyan died yesterday at 97 years of age. He was a brilliant logician (What is the Name of this Book?), mathematician, musician, and magician and challenged one's intellect in all his domains."

Am berühmtesten dürfte sein Knights and Knaves-Rätsel aus eben jenem Buch sein, in dem jeweils ein Ritter und ein Schurke entweder immer die Wahrheit sagen oder lügen. Die Door-Riddle-Szene aus Jim Hensons Labyrinth hat das Puzzle dann weltweit bekannt gemacht:

Hier die Auflösung:

To solve the puzzle, you must ask one guard (it doesn’t matter which one) which door the other guard would say leads out. Both guards will indicate the same door, which will be the door that doesn’t lead out. For purposes of this explainer, we’ll call the doors A (the safe door), and B (the knock, knock, knocking on heaven’s door). Let’s discuss:

  • Scenario one: The guard you ask is the one who lies.

    If the guard you asked is the one who lies, then he will lead you astray by telling you (falsely) that the other guard – the truthful guard – will point you towards door B. This makes door A the safe bet.

  • Scenario two: The guard you asked is the one who tells the truth.

    If the guard you ask is the one who tells the truth, he will tell you (honestly) that the other guard – the lying guard – will point you towards door B. This makes door A the safe bet.

In both cases, the outcome is the same. To stay alive, you must walk through the opposite door you’ve been told.