If he weighs the same as a duck, he's made of wood
Angry Mob: "We've found a witch, may we burn her?" King Bedevere: "Bring her forward." (Examines the girl) "How do you know she is a witch?" Angry Mob: "Well, she looks like one" The Witch: "They dressed me up like this.... and this isn't my nose, it's a false one." King Bedevere: "Did you dress her up like this?" Angry Mob: "NO...No.... a bit, a bit. We did do the nose" King Bedevere: "The nose....?" Angry Mob: "And the hat, but she is a witch. Look she's got a wart." King Bedevere: "What makes you think that she is a witch?" Angry Mob: "What, she turned me into a newt." King Bedevere: "A newt?" Angry Mob: "........... i got better." "BURN HER ANYWAY!!!! BURN HER!!!!" King Bedevere: "Quiet, quiet! There are ways of telling whether she is a witch." Angry Mob: "There are??? Are there??? Tell us. Tell us. Do they hurt?" King Bedevere: "Tell me, what do you do with witches?" Angry Mob: "Burn Them!" King Bedevere: "And what do you burn apart from witches?" Angry Mob: "More witches!" (peasant gets slapped) Angry Mob: "Wood!" King Bedevere: "So, why do witches burn?" Angry Mob: "Because they're made of... wood?" King Bedevere: "Good! So how do we tell whether she is made of wood?" Angry Mob: "Build a bridge out of her!" King Bedevere: "Ahh, but can you not also make bridges out of stone?" Angry Mob: "Oh ya." King Bedevere: "Tell me, Does wood sink in water?" Angry Mob: "No, no, it floats." Angry Mob: "Throw her into the pond!" King Bedevere: "What also floats in water?" Angry Mob: "Bread, apples, very small rocks, cider, gravy, cherries, mud, churches, lead..." King Arthur: "A duck!" King Bedevere: "Exactly! So, logically....." Angry Mob: "If she weighs the same as a duck, she's made of wood." King Bedevere: "And therefore?" Angry Mob: "A Witch!"