Logic affects our lives everyday. We use it both subconsciously and consciously to make decisions which can be as important as our careers, or as insignificant as what to eat for lunch. Logic can also be used in other ways. Ironically, others' bad logic can result in us learning something just as much as we learn from our own bad decisions. This is shown in Monty Python's Quest for the Holy Grail.
One example of this ironic use of logic is with the trial of the witch. In this trial, Monty Python uses deductive reasoning to conclude that the woman is a witch. By this, he is demonstrating how deductive reasoning is not always right. Just because wood burns like a witch and floats like a duck does not mean she is a witch. The conclusion that "if she weighs as much as a duck, she is a witch", therefore, is entirely false. Her weight, at no moment, is a subject of the argument. It is just thrown into the argument, along with the duck and the wood, to make a connection between her and the duck. From this we learn that an argument cannot be won by randomly connecting points until you have proven yours.
Another display of this ironic logic is with the Knights who say "Ni". They are an example of a Red Herring Argument. They attempt to distract Arthur and his men from their original task with meaningless quests and tasks. Monty Python places the task of "cutting down the greatest tree with a herring" to ironically relate to this type of logic. It could have been anything else, but the herring was used to relate to this type. From this, we learn that there will often be many things in life to sidetrack us.
The greatest display of ironic logic in the movie was the rabbit outside the Cave of Caerbannog. This is an excellent example of deductive logic. Arthur and his knights assume that, since all the little white rabbits they have seen were harmless, that the one guarding the cave would also be harmless. The comic...