Rene Descartes walks into a restaurant and sits down for dinner. The waiter comes over and asks if he’d like an appetizer.
“No thank you” says Descartes, “I’d just like to order dinner.”
“Would you like to hear our daily specials?” asks the waiter.
“No” says Descartes, getting impatient.
“Would you like a drink before dinner?” the waiter asks.
Descartes is insulted, since he’s a teetotaler.
“I think not!” he says indignantly, and POOF! He disappears.