This is not at all Christmassy, but it is one of my favourite little law stories. It involves the principle of a convertible argument – an argument that is very strong, but can be reversed and is just as strong for the other side.
It involves Ancient Greece, and a man named Protagoras (not the triangle guy). Protagoras was a philosopher but also a lawyer, and he made part of his living by teaching students in law.
A young man, Euathlus, approached Protagoras and asked Protagoras to teach him law. However, Euathlus had no money to pay for this tuition. They agreed that Euathlus should pay Protagoras when Euathlus won his first case in Court.
The training was completed, and Euathlus was giving clients advice but not appearing in Court. Time passed and it became apparent to Protagoras that Euathlus was never intending to take a case on in Court, and so he would never be paid.
Protagoras went to Court himself, saying that Euathlus should be ordered to pay him. His argument was short and beautiful (one could even say “sophisticated”, given that Protagoras was a Sophist)
“Let me tell you, most foolish of youths, that in either event you will have to pay what I am demanding, whether judgment be pronounced for or against you. For if the case goes against you, the money will be due me in accordance with the verdict, because I have won; but if the decision be in your favour, the money will be due me according to our contract, since you will have won a case.”
Euathlus had learned from the best though, and replied
“I might have met this sophism of yours, tricky as it is, by not pleading my own cause but employing another as my advocate. But I take greater satisfaction in a victory in which I defeat you, not only in the suit, but also in this argument of yours. So let me tell you in turn, wisest of masters, that in either event I shall not have to pay what you demand, whether judgment be pronounced for or against me. For if the jurors decide in my favour, according to their verdict nothing will be due you, because I have won; but if they give judgment against me, by the terms of our contract I shall owe you nothing, because I have not won a case.”
The jurors simply adjourned the decision indefinitely, probably because they recognised a Paradox when they saw one….
[Personally, I would make Euathlus pay, but it is damn difficult to construct a judgment to make it unappealable]