Monty Python and the Holy Grail1975

Sir Bedevere:
There are ways of telling whether she is a witch.

Peasant 1:
Are there? Oh well, tell us.

Sir Bedevere:
Tell me. What do you do with witches?

Peasant 1:
Burn them.

Sir Bedevere:
And what do you burn, apart from witches?

Peasant 1:
More witches.

Peasant 2:
Wood.

Sir Bedevere:
Good. Now, why do witches burn?

Peasant 3:
...because they're made of... wood?

Sir Bedevere:
Good. So how do you tell whether she is made of wood?

Peasant 1:
Build a bridge out of her.

Sir Bedevere:
But can you not also build bridges out of stone?

Peasant 1:
Oh yeah.

Sir Bedevere:
Does wood sink in water?

Peasant 1:
No, no, it floats!... It floats! Throw her into the pond!

Sir Bedevere:
No, no. What else floats in water?

Peasant 1:
Bread.

Peasant 2:
Apples.

Peasant 3:
Very small rocks.

Peasant 1:
Cider.

Peasant 2:
Gravy.

Peasant 3:
Cherries.

Peasant 1:
Mud.

Peasant 2:
Churches.

Peasant 3:
Lead! Lead!

King Arthur:
A Duck.

Sir Bedevere:
...Exactly. So, logically...

Peasant 1:
If she weighed the same as a duck... she's made of wood.

Sir Bedevere:
And therefore...

Peasant 2:
...A witch!