Parlor Wit

In this scene from Monty Python and The Holy Grail, we are shown the danger of applying scientific analysis to matters of religion. Here wise Sir Bedevere demonstrates to villagers how they may identify a witch. ;)

BEDEVERE: Quiet! Quiet! There are ways of telling whether she is a witch.
ALL: There are? Tell us. What are they, wise Sir Bedevere?
BEDEVERE: Tell me ... what do you do with witches?
ALL: Burn them.
BEDEVERE: And what do you burn, apart from witches?
FOURTH VILLAGER: ... Wood?
BEDEVERE: So why do witches burn?
SECOND VILLAGER: ... Because they're made of wood...?
BEDEVERE: Good.
ALL: I see. Yes, of course.
BEDEVERE: So how can we tell if she is made of wood?
FIRST VILLAGER: Make a bridge out of her.
BEDEVERE: Ah ... but can you not also make bridges out of stone?
ALL: Ah. Yes, of course ... um ... err ...
BEDEVERE: Does wood sink in water?
ALL: No, no. It floats. Throw her in the pond. Tie weights on her. To the pond.
BEDEVERE: Wait. Wait ... tell me, what also floats on water?
ALL: Bread? No, no, no. Apples .... gravy ... very small rocks ...
ARTHUR: A duck.
They all turn and look at ARTHUR. BEDEVERE looks up very impressed.
BEDEVERE: Exactly. So... logically ...
FIRST VILLAGER: (beginning to pick up the thread) If she ... weighs the same as a duck .... she's made of wood.
BEDEVERE: And therefore?
ALL: A witch! ... A duck! A duck! Fetch a duck!
http://www.montypythonpages.com/index1.htm