The Paradox of the Court, also known as the dilemma of Euathlus, is a very old problem. It is said that the sophist Protagoras took on a pupil, Euathlus, on the understanding that the student pay Protagoras for his lessons after he wins first court case. Protagoras decided to sue Euathlus for the amount owed.
Euathlus, however, claimed that if he won, then by the court's decision he would not have to pay Protagoras. If, on the other hand, Protagoras won, then Euathlus would still not have won a case and would therefore not be obliged to pay.