Descartes and Wittgenstein are on a Mediterranean cruise and they lean against the ship's railing and look thoughtfully at the seemingly endless expanse of the bluegreen sea.

After a long while Descartes speaks...

"Wittgenstein, clara voce cogito; visne scire quid credem? Credo 'cogito, ergo sum'."

Translation...
"Wittgenstein, I'm thinking out loud; you know what I think? I think that 'I think, therefore I am'."

To which Wittgenstein replied...

"Descartes, you pretentious dolt, can't you speak English?
You are presuming the "I" that does the thinking!"

Then Descartes and Wittgenstein both vanish in a puff of Wittgenstein's logic.