Bedevere: Tell me. What do you do with witches?
Crowd: Burn! Burn them up! Burn!...
Bedevere: And what do you burn apart from witches?
Villagers: More witches! Wood!
Bedevere: So, why do witches burn?
Villager: because they're made of wood?
Bedevere: So, how do we tell whether she is made of wood? Does wood sink in water?
Villager: No. No. No, it floats! It floats!
Bedevere: What also floats in water?
Arthur: A duck!
Bedevere: Exactly. So, logically...
Villager: If... she... weighs... the same as a duck,... she's made of wood.
Bedevere: And therefore?
Villager: A witch!