Sir Bedevere: There are ways of telling whether she is a witch.
-—Are there? Oh well, tell us.
Sir Bedevere: Tell me. What do you do with witches?
—Burn them.
Sir Bedevere: And what do you burn, apart from witches?
—More witches.
—Wood.
Sir Bedevere: Good. Now, why do witches burn?
—...because they’re made of... wood?
Sir Bedevere: Good. So how do you tell whether she is made of wood?
—Build a bridge out of her.
Sir Bedevere: But can you not also build bridges out of stone?
—Oh yeah.
Sir Bedevere: Does wood sink in water?
—No, no, it floats!... It floats! Throw her into the pond!
Sir Bedevere: No, no. What else floats in water?
—Bread.
—Apples.
—Very small rocks.
—Cider.
—Gravy.
—Cherries.
—Mud.
—Churches.
—Lead! Lead!
—A Duck.
Sir Bedevere: ...Exactly. So, logically...
—If she weighed the same as a duck... she’s made of wood.
Sir Bedevere: And therefore...
...A witch!