Prolog - Sir Bedevere, Monty Python.

After 'Monty Python and the Holy Grail' (1975). 

witch(X)  <= burns(X) and female(X).

burns(X)  <= wooden(X).

wooden(X) <= floats(X).
wooden(woodBridge).
stone(stoneBridge).

floats(bread).
floats(apple).
floats(cherry).
floats(X) <= sameweight(duck, X).

female(girl).          {by observation}
sameweight(duck,girl). {by experiment }

? witch(girl).

{ After Monty Python (Sir Bedevere). }
A witch is a female who burns. Witches burn – because they're made of wood. Wood floats. What else floats on water? A duck; if something has the same weight as a duck it must float. A duck and scales are fetched. The girl and the duck balance perfectly. "It's a fair cop."



Monty Python and the Holy Grail (1975)
The witchConnie Booth
Sir Bedevere (etc.)Terry Jones
King ArthurGraham Chapman
Mr. Blint (a village n'er do well very keen on burning witches) (etc.) Eric Idle
Mr. Newt (a village blacksmith quite interested in burning witches) (etc.) John Cleese
Mr. Duck (a village carpenter who is almost keener than anyone else to burn witches) (etc.) Michael Palin
Directed byTerry Gilliam, Terry Jones
— must be © the Pythons