Vizzini: I can't compete with you physically, and you're no match for my brains.
Man in Black: [intrigued] You're that smart?
Vizzini: Let me put it this way: Have you ever heard of Plato? Aristotle? Socrates?
Man in Black: Yes.
Man in Black: Really? In that case, I challenge you to a battle of wits.
Vizzini: For the princess? [The Man in Black nods] To the death? [He nods] I accept.
Man in Black: Good. Then pour the wine. [Vizzini pours the wine, and the Man in Black pulls out a small packet] Inhale this, but do not touch.
Vizzini: [sniffs] I smell nothing.
Man in Black: What you do not smell is called iocane powder. It is odorless, tasteless, dissolves instantly in liquid, and is among the more deadlier poisons known to man.
[He puts the goblets behind his back and, presumably, adds the poison to one of them, then sets them down in front of him]
Man in Black: All right. Where is the poison? The battle of wits has begun. It ends when you decide and we both drink, and find out who is right... and who is dead.
Vizzini: But it's so simple. All I have to do is divine from what I know of you: are you the sort of man who would put the poison into his own goblet or his enemy's? Now, a clever man would put the poison into his own goblet, because he would know that only a great fool would reach for what he was given. I am not a great fool, so I can clearly not choose the wine in front of you. But you must have known I was not a great fool. You would have counted on it, so I can clearly not choose the wine in front of me.
Man in Black: You've made your decision then?
Vizzini: Not remotely! Because iocane comes from Australia, as everyone knows! And Australia is entirely peopled with criminals. And criminals are used to having people not trust them, as you are not trusted by me, so I can clearly not choose the wine in front of you.
Man in Black: Truly, you have a dizzying intellect.
Vizzini: Wait till I get going! Now, where was I?
Man in Black: Australia.
Vizzini: Yes, Australia. And you must have suspected I would have known the powder's origin, so I can clearly not choose the wine in front of me.
Man in Black: You're just stalling now.
Vizzini: You'd like to think that, wouldn't you?! You've beaten my giant, which means you're exceptionally strong, so you could've put the poison in your own goblet, trusting on your strength to save you, so I can clearly not choose the wine in front of you! But, you've also bested my Spaniard, which means you must have studied, and in studying you must have learned that man is mortal, so you would have put the poison as far from yourself as possible, so I can clearly not choose the wine in front of me!
Man in Black: You're trying to trick me into giving away something. It won't work.
Vizzini: It has worked! You've given everything away! I know where the poison is!
Man in Black Then make your choice.
Vizzini: I will, and I choose- What in the world can that be? [Vizzini points at a rock behind the Man in Black. When he turns to look, Vizzini swaps the goblets]
Man in Black: What? Where? I don't see anything.
Vizzini: Well, I- I could have sworn I saw something. No matter. [He is having a hard time containing his laughter]
Man in Black: What's so funny?
Vizzini: I--I'll tell you in a minute. First, let's drink. Me from my glass, and you from yours. [They drink from their goblets]
Man in Black: You guessed wrong.
Vizzini: You only think I guessed wrong! That's what's so funny! I switched glasses when your back was turned! Ha ha, you fool! You fell victim to one of the classic blunders! The most famous of which 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!" [He laughs hysterically, but suddenly freezes mid-laugh and dies; the Man in Black removes Buttercup's blindfold]
Buttercup: Who are you?
Man in Black: I am no one to be trifled with. That is all you ever need know.
Buttercup: And to think, all that time it was your cup that was poisoned.
Man in Black: They were both poisoned. I spent the last few years building up an immunity to iocane powder.