Monty Python and the Holy Grail

"how do you know she is a witch" "She looks like one" "I'm not a witch! I'M not a witch! They dressed me up like this and this isn't my nose it's a false one." "I see. Eh.. Did you dress her up like this?" "Well, nose a bit. Yeah a bit." "Tell me. What do you do with witches?" "Burn them! Burn!" "And then why do witches burn. Hmmm.." "Because they're, made of wood?" "So how do you tell if she is made of wood?" "Eh.. Build a bridge out of 'er" "But can not you also build bridges out of stone?" "Oh yeah" "Does wood sink in water?" "No no it floats. Throw her into the pond!" "Wait! What also floats in water?" "Umm.. very small rocks. churches. lead!" "A duck" "presicly!" "So logically.." "If she weighs the same as a duck, then shes made outta wood." "And therefore" "She's a witch!"