The Paradox of the Court, also known as the counter dilemma of Euathlus, is a very old problem from ancient Greece.
Many years ago, famous sophist Protagoras came across Euathlus, who was willing to learn from Protagoras. But Euathlus doesn’t have enough money to pay Protagoras, so they made a deal. According to the deal Euathlus pay Protagoras for his instruction after he wins his first court case. After instruction, Euathlus decided to not enter the profession of law. Protagoras started asking Euathlus to pay up the fee, but Euathlus reminded him of the deal according to which he will pay only after he wins his first court case.
Fed up with this, the teacher decided to sue the student in the court of law.
Protagoras argument : “Let me tell you that in either event, whether I win the case or lose the case, you will have to pay what I am demanding. Because, if I win the case, you have to pay the money according to the judgement. If I lose the case, you still need to pay according to the original contract, because you have won your first case”.
Euathlus argued back saying: “So let me tell you in turn, that in either event I shall not have to pay what you demand, whether I win the case or lose the case. Because, if I win, then by the court’s decision I would not have to pay you. If, on the other hand, if I lose, then I would still not have won a case and according to the agreement I would not have to pay you”.
This is one of the greatest paradoxes ever recorded.
Source: Paradox of the Court