"The Princess Bride"
by William Goldman.
Vizzini tries to decide which glass contains the poison in his battle of wits with Westley.
Guess?....I don't guess. I think. I ponder. I deduce. Then I decide. But I never guess....It's all so simple....All I have to do is deduce, from what I know of you, the way your mind works. Are you the kind of man who would put the poison into his own glass, or into the glass of his enemy?...Now a great fool....would place the wine in his own goblet, because he would know that only another great fool would reach first for what he was given. I am clearly not a great fool, so I will clearly not reach for your wine....[But] you knew I was not a great fool, so you would know that I would never fall for such a trick. You would count on it. So I will clearly not reach for mine either....We have now decided that the poisoned cup is most likely in front of you. But the poison is powder made from iocane and iocane comes only from Australia and Australia, as everyone knows, is peopled with criminals and criminals are used to having people not trust them, as I don't trust you, which means I can clearly not choose the wine in front of you....But, again, you must have suspected I knew the origins of iocane, so you would have known I knew about the criminals and criminal behavior, and therefore I can clearly not choose the wine in front of me....You have beaten my Turk, which means you are exceptionally strong, and exceptionally strong men are convinced that they are too powerful ever to die, too powerful even for iocane poison, so you could have put it in your cup, trusting on your strength to save you; thus I can clearly not choose the wine in front of you....But you also bested my Spaniard, which means you must have studied, because he studied many years for his excellence, and if you can study, you are clearly more than simply strong; you are aware of how mortal we all are, and you do not wish to die, so you would have kept the poison as far from yourself as possible; therefore I can clearly not choose the wine in front of me....I have already learned everything from you....I know where the poison is....What in the world can that be?....I could have sworn I saw something, no matter....Let's drink....[I guessed wrong?] You only think I guessed wrong....I switched glasses when your back was turned....Fool!....You fell victim to one of the classic blunders. The most famous is 'Never get involved in a land war in Asia,' but only slightly less well known is this: 'Never go in against a Sicilian when death is on the line.' (As he laughs, he keels over dead from the poison.)